FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 1
CHƢƠNG 5. PHÂN S(TP2).
BÀI 1. PHÂN S VI T VÀ MU LÀ CÁC S NGUYÊN.
I. M RNG KHÁI NIM PHÂN S:
Khi ta thc hin phép chia s nguyên a cho s nguyên b khác 0 ta được phân s
a
b
.
Khi đó: a gọi là t s, b gi là mu s. Đọc là a phn b.
Chú ý: Mi s nguyên cũng được coi là mt phân s vi mu là 1
II. PHÂN S BNG NHAU. Hai phân s
a
b
c
d
bng nhau nếu
a.d b.c
.
-----------------------------------------------------------------------------------------------------------
III. BÀI TP VN DNG.
Dng 1: Nhn dng phân s
Bài 1: Viết và đọc các phân s trong mi trường hp sau:
a) T s
43
, mu s là 19.
b) T s là -123 , mu s -63
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 2: Viết các phép chia sau dưới dng phân s và cho biết t s, mu s:
a)
6:1
.
b)
9: 4
.
c)
7: 3
.
d)
3: 4
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 3: Viết các s nguyên sau dng phân s: 2;
5
, 0;
.........................................................................................................................................................................
.........................................................................................................................................................................
Dng 2: Tìm hiu v hai phân s bng nhau.
Bài 1: Các phân s sau có bng nhau hay không?
a)
4
8
1
2
.
b)
1
6
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 2
.........................................................................................................................................................................
Bài 2: Các cp phân s sau có bng nhau hay không? Vì sao?
a)
2
9
.
b)
1
5
4
25
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 3: Các cp phân s sau đây có bằng nhau hay không?
a)
3
10
b)
4
9
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Dng 3: Tìm x trong hai phân s bng nhau.
Bài 1: Tìm s nguyên x biết:
a)
6 18
5x
.
b)
3 21
4x
.
c)
2 18
7x
.
d)
5 10
2x
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 2: Tìm s nguyên x biết:
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 3
a)
x6
7 21
.
b)
x1
12 6
.
c)
1x
2 12
.
d)
x 21
4 28
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 3: Tìm s nguyên x biết:
a)
7x
6 12
.
b)
5x
4 12
.
c)
3 18
11 x
.
d)
x6
7 21
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 4: Tìm các s nguyên x, y sao cho
4 x 40
11 22 y

.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 5: Tìm các s nguyên x, y tha mãn
3 x 21
4 20 y
.
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 4
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 6: Tìm các s nguyên x, y, z tha mãn
4 x 7 z
8 10 y 24


.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 7: Tìm s nguyên x biết:
a)
x 12
7 28
.
b)
x 12
5 10
.
c)
30 24
x 16
.
d)
36
x 14

.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 8: Tìm x biết:
a)
27 12
x
34

.
b)
28 21
x
47


.
c)
21 12
x
76


.
d)
30 28
x
6 14


.
e)
36 15
x
95


.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 5
BÀI 2. TÍNH CHẤT CƠ BẢN CA PHÂN S.
I. TÍNH CHT.
Nếu nhân ca tmu ca mt phân s vi cùng mt s nguyên khác 0 thì ta đc
mt phân s mi bng phân s đã cho.
Tng quát:
a a.m
b b.m
.
Áp dng tính chất trên để ta có th quy đồng mu hai phân s.
Nếu chia c t và mu ca mt phân s cho cùng một ước chung ca chúng thì ta
đưc mt phân s mi bng phân s đã cho.
Tng quát:
a a :n
b b :n
vi n là một ước chung ca a và b.
Áp dng tính cht trên ta có th rút gn phân s bng cách chia cho UCLN.
Chú ý: Ta có th đưa dấu “ i mu lên trên t hoc ra ngoài phân s.
C th
a a a
b b b
.
-----------------------------------------------------------------------------------------------------------
II. BÀI TP VN DNG
Dng 1: Rút gn phân s.
Bài 1: Tìm mt phân s bng mi phân s sau:
21
13
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 2: Rút gn các phân s sau:
132
264
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 3: Rút gn các phân s sau:
9
27
22
55
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 6
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 4: Rút gn các phân s sau v phân s ti gin:
450
540
390
240
2020
2024
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 5: Viết s đo thời gian sau đây theo đơn vị giờ, dưới dng phân s ti gin.
a) 15 phút.
b) 90 phút.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 6: Dùng phân s có mu s dương nhỏ nhất để biu th xem s phút sau đây chiếm
bao nhiêu phn ca mt gi?
a) 15 phút.
b) 20 phút.
c) 45 phút.
d) 50 phút.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 7: Dùng phân s để viết mi khối lượng sau theo t.
a) 20kg.
b) 55kg.
c) 87kg.
d) 91kg.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 7
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 8: Gii thích vì sao hai phân s sau bng nhau bng hai cách.
a)
8
14
1
21
.
b)
5
11
.
c)
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 9: Rút gn các phân s sau:
a)
11.4 11
2 13
b)
8.5 8.2
16
c)
153.24 153.11
7 160
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 10: Rút gn các phân s sau: a)
3.5
8.24
b)
2.14
7.8
c)
3.7.11
22.9
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 11: Rút gn các phân s sau:
a)
3 2 2
2 3 2 3
2 .3 2.3.5
b)
2 .3 3 .5
.
.........................................................................................................................................................................
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 8
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Dạng 2. Quy đồng mu các phân s.
Bài 1: Quy đồng mu hai phân s sau:
a)
5
5
8
7
.
b)
4
7
8
9
.
c)
2
9
4
7
.
d)
3
5
5
6
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 2: Quy đồng mu hai phân s sau:
a)
5
14
1
21
.
b)
5
6
2
9
.
c)
3
10
5
21
.
d)
13
24
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 9
.........................................................................................................................................................................
Bài 3: Quy đồng mu hai phân s sau:
a)
3
16
5
24
.
b)
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 4: Quy đồng mu s các phân s sau:
a)
b)
9
15
.
c)
1
360
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 5: Quy đồng mu s các phân s sau:
a)
1
3
;
1
2
2
3
.
b)
3
4
;
1
6
5
6
.
c)
1
3
;
1
2
2
3
.
d)
1
3
;
1
5
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 10
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 6: Quy đồng mu s các phân s sau:
a)
2
3
;
5
9
7
12
.
b)
3
7
;
8
15
4
21
.
c)
11
5
;
7
15
.
d)
5
6
;
2
5
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 7: Một vòi nước chy vào mt b không có ớc, sau 40 phút thì đầy b. Hi sau 10
phút, lượng nước đã chảy chiếm bao nhiêu phn b.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 8: Hà Linh tham gia mt cuc thi sáng tác và nhận được phn thưởng là s tin 200
000 đồng. Bn mua một món quà để tng sinh nht m hết 80 000 đồng. Hỏi Hà Linh đã
tiêu hết bao nhiêu phn s tiền mình được thưởng?
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 11
BÀI 3. SO SÁNH CÁC PHÂN S. HN S DƢƠNG
I. SO SÁNH CÁC PHÂN S.
Vi hai phân s có mu có cùng mt mẫu dương, phân số nào có t lớn hơn thì ln
hơn.
Vi hai phân s không cùng mẫu, ta đưa chúng về cùng mt mẫu dương rồi so
sánh.
Chú ý:
+ Phân s dương là phân s lớn hơn 0.
+ Phân s âm là phân s nh hơn 0.
+ Nếu
ac
bd
ce
dg
thì
ae
bg
.
-----------------------------------------------------------------------------------------------------------
II. BÀI TP VN DNG.
Dng . So sánh phân s.
Bài 1: So sánh: (cùng mu)
a)
.
b)
15
1001
12
1001
.
c)
401
801
104
801
.
d)
125
2021
152
2021
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 2: So sánh: (cách gii: so sánh vi s 0)
a)
9
4
1
3
.
b)
2
5
3
5
.
c)
2
3
2
5
.
d)
21
10
5
2
.
.........................................................................................................................................................................
.........................................................................................................................................................................
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 12
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 3: So sánh: ( quy đồng)
a)
4
5
3
7
.
b)
5
3
5
2
.
c)
8
3
4
7
.
d)
3
7
4
9
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 4: So sánh: ( Phn bù)
a)
47
57
66
76
.
b)
551
554
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 5: So sánh: ( quy đồng)
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 13
a)
5
8
4
7
.
b)
3
4
3
7
.
c)
4
15
.
d)
3
20
2
15
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 6: So sánh:
a)
31
15
và 2.
b)
3
7
2
.
c)
501
101
5
.
d)
12
145
12
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 7:
a) Sp xếp các s sau theo th t tăng dần
2
5
;
1
2
;
2
7
.
b) Sp xếp các s sau theo th t gim dn
12
5
;
7
3
;
11
4
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 14
.........................................................................................................................................................................
Bài 8:
a) Sp xếp các s sau theo th t tăng dần
4
;
10
3
;
9
2
.
b) Sp xếp các s sau theo th t gim dn
25
6
;
; 4 và
31
8
.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 9: Tìm s t nhiên x sao cho :
a)
1 x 1
8 40 5

. b)
3 x 2
7 7 7

. c)
4 x 1
3 3 3


. d)
1 x 1
8 72 36


.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 10: Lp 6A có
4
5
s hc sinh thích bóng bàn,
7
10
s học sinh thích bóng đá và
1
2
s
hc sinh thích bóng chuyn. Hi môn th thao nào được các bn hc sinh lp 6A yêu
thích nht?
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 11: Bn Vit là một người rất thích đi xe đạp vào cui tun. Ngày th by, bạn đi
đưc 31km trong 2 gi. Ngày Ch nht, bạn đi được 46km trong 3 gi. Hi ngày nào bn
Việt đạp xe nhanh hơn?
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 15
BÀI 4. PHÉP CNG, TR PHÂN S.
1. PHÉP CNG PHÂN S.
Mun cng hai phân s có cùng mu, ta cng t sgi nguyên mu.
Tng quát:
a b a b
m m m

.
Mun cng hai phân s không cùng mẫu, ta quy đồng mu ca chúng ri tính.
Phép cng các phân s có đầy đ các tính cht giao hoán và kết hp.
2. PHÉP TR PHÂN S. Hai phân s gọi là đối nhau nếu tng ca chúng bng 0.
Mun tr mt phân s cho mt phân s, ta ly phân s th nht cng vi s đối
ca phân s th hai.
a b a b a ( b)
m m m m
3. CNG HAI PHÂN S KHÁC MU.
Cách 1: Quy đồng đƣa về hai phân s cùng mu
Cách 2: Nhân chéo chia ngang
a c ad bc
b d bd

4. TÍNH CHT CA PHÂN S
Tính cht giao hoán:
a c c a
b d d b
Tính cht kết hp
a c e a c e
( ) ( )
b d f b d f
Ký hiu s đối ca
a
b
a a a
b b b
5. QUY TC DU NGOC.
Khi b du ngoc có dấu “+” đằng trước, ta gi nguyên du các s hng trong
ngoc.
Khi b du có du “–” đằng trước, ta đi du tt c các s hng trong ngoc.
-------------------------------------------------------------------------------------------------------
6. BÀI TP VN DNG.
Dng 1: Tìm s đối ca mt s
Bài 1: Tìm s đối ca mi phân s sau:
10
9
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Dng 2: Tính
Bài 1: Tính: ( cùng mu)
a)
15
66
b)
37
55
c)
35
88

d)
78
25 25
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 16
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 2: Tính:
a)
14
55
b)
12
33
c)
32
77
d)
75
12 12
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 3: Tính:
a)
79
10 10
b)
19
13 13
c)
57
33

d)
71
99

.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 4: Tính: ( mu chung là mu ln)
a)
11
82
b)
35
48
c)
51
10 2
d)
45
9 18
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 17
.........................................................................................................................................................................
Bài 5: Tính:
a)
35
4 12
b)
76
15 5
c)
13 5
20 2
d)
51
63
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 6: Tính: (mu có chung tha s)
a)
58
69
b)
11 1
64
c)
35
8 12
d)
55
16 24
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 7: Tính:
a)
35
8 12
b)
79
12 20
c)
11
21 28

d)
43
8 10

.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 8: Tính:
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 18
a)
1 13
6 15

b)
18 15
24 21
c)
11 17
12 18
d)
13 14
10 25
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 9: Tính:
a)
51
73
b)
32
85
c)
11
16 15
d)
23
54

.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 10: Tính: (s nguyên vi phân s)
a)
3
1
4
b)
1
1
2
c)
1
2
5
d)
1
5
6

.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 11: Tính:
a)
2
3
7

b)
2
3
5

c)
2
3
3

d)
5
4
7

FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 19
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 12: Tính:
a)
4
2
5



b)
5
( 2)
8

c)
3
3
4

d)
3
6
20




.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 13: Tính hp lí:
a)
5 5 2 2
12 3 12 3
b)
5 12 13 2
8 7 8 7
c)
2 3 3 13
5 8 5 8

.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 14: Tính hp lí:
a)
2 3 7
9 10 10


b)
3 5 4
7 13 7


c)
11 2 1
6 5 6


FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
FanPage: Thy Thanh chuyên Toán. Toán Hc Tr Hàm Rng Biên Hòa 20
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 15: Tính hp lí:
a)
54
2
99




b)
56
1
11 11





c)
67
1
13 13





.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 16: Tính hp lí:
a)
3 2 1
5 7 5





b)
2 5 4
5 6 5






c)
14 1 19
13 13 20




.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 17: Tính hp lí:
a)
2 47 5
49 49 3




b)
24 7 1
17 17 16





c)
7 5 13
18 12 18





.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................

Preview text:

FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
CHƢƠNG 5. PHÂN SỐ(TẬP2).
BÀI 1. PHÂN SỐ VỚI TỬ VÀ MẪU LÀ CÁC SỐ NGUYÊN.
I. MỞ RỘNG KHÁI NIỆM PHÂN SỐ:  a
Khi ta thực hiện phép chia số nguyên a cho số nguyên b khác 0 ta được phân số . b
 Khi đó: a gọi là tử số, b gọi là mẫu số. Đọc là a phần b.
Chú ý: Mỗi số nguyên cũng được coi là một phân số với mẫu là 1 a c
II. PHÂN SỐ BẰNG NHAU. Hai phân số và bằng nhau nếu a.d  b.c. b d
-----------------------------------------------------------------------------------------------------------
III. BÀI TẬP VẬN DỤNG.

Dạng 1: Nhận dạng phân số
Bài 1:
Viết và đọc các phân số trong mỗi trường hợp sau: a) Tử số là 43  , mẫu số là 19.
b) Tử số là -123 , mẫu số -63
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 2: Viết các phép chia sau dưới dạng phân số và cho biết tử số, mẫu số: a) 6  :1. b) 9 :  4   . c) 7 :  3   . d) 3  :  4   .
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 3: Viết các số nguyên sau ở dạng phân số: 2; 5  , 0;
.........................................................................................................................................................................
.........................................................................................................................................................................
Dạng 2: Tìm hiểu về hai phân số bằng nhau.
Bài 1:
Các phân số sau có bằng nhau hay không? 4 1 a) và . 8 2 1 3  b) và 6 18 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 1
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
.........................................................................................................................................................................
Bài 2: Các cặp phân số sau có bằng nhau hay không? Vì sao? 2 6 a) và . 9 27  1 4 b) và . 5 25
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 3: Các cặp phân số sau đây có bằng nhau hay không? 12  3 a) và 35 10 4 20  b) và . 9 45
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Dạng 3: Tìm x trong hai phân số bằng nhau.
Bài 1: Tìm số nguyên x biết: 6 18 a)  . 5 x 3 2  1 b)  . 4 x 2 18 c)  . 7  x 5 10 d)  . 2 x
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 2: Tìm số nguyên x biết:
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 2
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908 x 6 a)  . 7 21 x 1 b)  . 12 6 1 x c)  . 2 12 x 21 d)  . 4 28
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 3: Tìm số nguyên x biết: 7  x a)  . 6 12 5 x b)  . 4  12 3 18 c)  . 11 x x 6 d)  . 7 21
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... 4 x 40
Bài 4: Tìm các số nguyên x, y sao cho   . 11 22 y
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... 3 x 21
Bài 5: Tìm các số nguyên x, y thỏa mãn    . 4 20 y
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 3
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... 4 x 7 z
Bài 6: Tìm các số nguyên x, y, z thỏa mãn    . 8 1  0 y 2  4
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 7: Tìm số nguyên x biết: x 12  a)  . 7 28 x 12  b)  . 5 10 30 24 c)  . x 16 3  6 d)   . x 14 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... Bài 8: Tìm x biết: 27  12 a)  x  . 3 4 2  8 2  1 b)  x  . 4 7 2  1 1  2 c)  x  . 7 6 30  28  d)  x  . 6 14 36  15  e)  x  . 9 5
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 4
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
BÀI 2. TÍNH CHẤT CƠ BẢN CỦA PHÂN SỐ. I. TÍNH CHẤT.
 Nếu nhân của tử và mẫu của một phân số với cùng một số nguyên khác 0 thì ta đực
một phân số mới bằng phân số đã cho.  a a.m Tổng quát:  . b b.m
 Áp dụng tính chất trên để ta có thể quy đồng mẫu hai phân số.
 Nếu chia cả tử và mẫu của một phân số cho cùng một ước chung của chúng thì ta
được một phân số mới bằng phân số đã cho.  a a : n Tổng quát: 
với n là một ước chung của a và b. b b : n
 Áp dụng tính chất trên ta có thể rút gọn phân số bằng cách chia cho UCLN.
Chú ý: Ta có thể đưa dấu “ – ” ở dưới mẫu lên trên từ hoặc ra ngoài phân số. a a a Cụ thể    . b b b
-----------------------------------------------------------------------------------------------------------
II. BÀI TẬP VẬN DỤNG
Dạng 1: Rút gọn phân số. 21 12 18 42 
Bài 1: Tìm một phân số bằng mỗi phân số sau: 13 25  48  24 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... 12 39  132
Bài 2: Rút gọn các phân số sau: 24  75 264
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... 12  7 9 22 25 
Bài 3: Rút gọn các phân số sau: 4  35  27 55 75 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 5
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... 450 390 2020
Bài 4: Rút gọn các phân số sau về phân số tối giản: 540 240 2024
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 5: Viết số đo thời gian sau đây theo đơn vị giờ, dưới dạng phân số tối giản. a) 15 phút. b) 90 phút.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 6: Dùng phân số có mẫu số dương nhỏ nhất để biểu thị xem số phút sau đây chiếm
bao nhiêu phần của một giờ? a) 15 phút. b) 20 phút. c) 45 phút. d) 50 phút.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 7: Dùng phân số để viết mỗi khối lượng sau theo tạ. a) 20kg. b) 55kg. c) 87kg. d) 91kg.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 6
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 8: Giải thích vì sao hai phân số sau bằng nhau bằng hai cách. 8 1 a) và . 14 21 15  5 b) và . 33 11 7 35 c) và . 12  60 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 9: Rút gọn các phân số sau: 11.4 11 8.5  8.2 153.24 153.11 a) b) c) 2 13 16 7 160
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... 3.5 2.14 3.7.11
Bài 10: Rút gọn các phân số sau: a) b) c) 8.24 7.8 22.9
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 11:
Rút gọn các phân số sau: 3 2 2 2 .3 2.3.5 a) b) . 2 3 2 3 2 .3 3 .5
.........................................................................................................................................................................
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 7
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Dạng 2. Quy đồng mẫu các phân số.
Bài 1:
Quy đồng mẫu hai phân số sau: 5 8 a) và . 5 7 4 8 b) và . 7 9 2 4 c) và . 9 7 3 5 d) và . 5 6
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 2: Quy đồng mẫu hai phân số sau: 5 1 a) và . 14 21 5 2 b) và . 6 9 3 5 c) và . 10 21 13 7 d) và . 24 30 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 8
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
.........................................................................................................................................................................
Bài 3: Quy đồng mẫu hai phân số sau: 3 5 a) và . 16 24 3 11  b) và . 20  30 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 4: Quy đồng mẫu số các phân số sau: 11 17  a) và 12  18 9 17 b) và . 15 20  7 1 c) và 240 360
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 5: Quy đồng mẫu số các phân số sau: 1 1 2 a) ; và . 3 2 3 3 1 5 b) ; và . 4 6 6 1  1  2 c) ; và . 3 2 3 1 1  1 d) ; và . 3 5 10 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 9
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 6: Quy đồng mẫu số các phân số sau: 2 5 7 a) ; và . 3 9 12 3 8 4 b) ; và . 7 15 21 11 23 7 c) ; và . 5 30  15 5 2 7 d) ; và . 6 5 12 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 7: Một vòi nước chảy vào một bể không có nước, sau 40 phút thì đầy bể. Hỏi sau 10
phút, lượng nước đã chảy chiếm bao nhiêu phần bể.
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 8: Hà Linh tham gia một cuộc thi sáng tác và nhận được phần thưởng là số tiền 200
000 đồng. Bạn mua một món quà để tặng sinh nhật mẹ hết 80 000 đồng. Hỏi Hà Linh đã
tiêu hết bao nhiêu phần số tiền mình được thưởng?
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 10
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
BÀI 3. SO SÁNH CÁC PHÂN SỐ. HỖN SỐ DƢƠNG
I. SO SÁNH CÁC PHÂN SỐ.
 Với hai phân số có mẫu có cùng một mẫu dương, phân số nào có tử lớn hơn thì lớn hơn.
 Với hai phân số không cùng mẫu, ta đưa chúng về cùng một mẫu dương rồi so sánh. Chú ý:
+ Phân số dương là phân số lớn hơn 0.
+ Phân số âm là phân số nhỏ hơn 0. a c c e a e + Nếu  và  thì  . b d d g b g
-----------------------------------------------------------------------------------------------------------
II. BÀI TẬP VẬN DỤNG.
Dạng . So sánh phân số.
Bài 1: So sánh: (cùng mẫu) 34 43 a) và . 77  77  15 12 b) và . 1001 1001 401 104 c) và . 801 801 125 152 d) và . 2021 2021
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 2: So sánh: (cách giải: so sánh với số 0) 9 1 a) và . 4 3 2 3 b) và . 5 5 2 2 c) và . 3 5 21 5 d) và . 10 2
.........................................................................................................................................................................
.........................................................................................................................................................................
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 11
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 3: So sánh: ( quy đồng) 4 3 a) và . 5 7 5 5 b) và . 3 2 8 4 c) và . 3 7 3 4 d) và . 7 9
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 4: So sánh: ( Phần bù) 47 66 a) và . 57 76 223 551 b) và . 226 554
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 5: So sánh: ( quy đồng)
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 12
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908 5 4 a) và . 8 7 3 3 b) và . 4 7 11 4 c) và . 42  15 3 2 d) và . 20 15
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... Bài 6: So sánh: 31 a) và 2. 15 7 b) 3  và . 2 501 c) và  5  . 101 145 d) 12  và 12
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... Bài 7: 2 1  2
a) Sắp xếp các số sau theo thứ tự tăng dần ; ; . 5 2 7 12 7 11
b) Sắp xếp các số sau theo thứ tự giảm dần ; ; . 5 3 4
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 13
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
......................................................................................................................................................................... Bài 8: 10 9 22 
a) Sắp xếp các số sau theo thứ tự tăng dần 4 ; ; và . 3 2 7  25 47  31
b) Sắp xếp các số sau theo thứ tự giảm dần ; ; 4 và . 6 12  8
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 9: Tìm số tự nhiên x sao cho : 1 x 1 3  x 2 4 x 1 1  x 1  a)   . b)   . c)   . d)   . 8 40 5 7 7 7 3  3  3 8 72 36
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... 4 7
Bài 10: Lớp 6A có số học sinh thích bóng bàn,
số học sinh thích bóng đá và 1 số 5 10 2
học sinh thích bóng chuyền. Hỏi môn thể thao nào được các bạn học sinh lớp 6A yêu thích nhất?
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 11: Bạn Việt là một người rất thích đi xe đạp vào cuối tuần. Ngày thứ bảy, bạn đi
được 31km trong 2 giờ. Ngày Chủ nhật, bạn đi được 46km trong 3 giờ. Hỏi ngày nào bạn Việt đạp xe nhanh hơn?
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 14
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
BÀI 4. PHÉP CỘNG, TRỪ PHÂN SỐ.
1. PHÉP CỘNG PHÂN SỐ.

 Muốn cộng hai phân số có cùng mẫu, ta cộng tử số và giữ nguyên mẫu.  a b a  b Tổng quát:   . m m m
 Muốn cộng hai phân số không cùng mẫu, ta quy đồng mẫu của chúng rồi tính.
 Phép cộng các phân số có đầy đủ các tính chất giao hoán và kết hợp.
2. PHÉP TRỪ PHÂN SỐ. Hai phân số gọi là đối nhau nếu tổng của chúng bằng 0.
 Muốn trừ một phân số cho một phân số, ta lấy phân số thứ nhất cộng với số đối a b a  b a  (b) của phân số thứ hai.    m m m m
3. CỘNG HAI PHÂN SỐ KHÁC MẪU.
Cách 1: Quy đồng đƣa về hai phân số cùng mẫu…
a c ad  bc
Cách 2: Nhân chéo chia ngang   b d bd
4. TÍNH CHẤT CỦA PHÂN SỐ a c c a
Tính chất giao hoán:    b d d b a c e a c e
Tính chất kết hợp (  )    (  ) b d f b d f a aa a
Ký hiệu số đối của là    b b b b
5. QUY TẮC DẤU NGOẶC.
 Khi bỏ dấu ngoặc có dấu “+” đằng trước, ta giữ nguyên dấu các số hạng trong ngoặc.
 Khi bỏ dấu có dấu “–” đằng trước, ta đổi dấu tất cả các số hạng trong ngoặc.
-------------------------------------------------------------------------------------------------------
6. BÀI TẬP VẬN DỤNG.
Dạng 1: Tìm số đối của một số
Bài 1:
Tìm số đối của mỗi phân số sau: 15  22 10 45  7 25  9 27 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... Dạng 2: Tính
Bài 1:
Tính: ( cùng mẫu) 1 5 3 7 3 5 7 8  a)  b)  c)  d)  6 6 5 5 8  8 2  5 25
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 15
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... Bài 2: Tính: 1 4 1 2 3 2 7  5 a)  b)  c)  d)  5 5 3 3 7 7 12 12
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... Bài 3: Tính: 7 9 1  9 5 7 7 1 a)  b)  c)  d)  10 10 13 13 3 3 9 9
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 4: Tính: ( mẫu chung là mẫu lớn) 1 1 3 5 5 1 4 5 a)  b)  c)  d)  8 2 4 8 10 2 9 18
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 16
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
......................................................................................................................................................................... Bài 5: Tính: 3 5 7 6 13 5 5 1 a)  b)  c)  d)  4 12 15 5 20 2 6 3
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 6: Tính: (mẫu có chung thừa số) 5 8 11 1 3 5 5 5 a)  b)  c)  d)  6 9 6 4 8 12 16 24
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... Bài 7: Tính: 3 5 7 9 1  1  4  3  a)  b)  c)  d)  8 12 12 20 21 28 8 10
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... Bài 8: Tính:
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 17
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908 1 13 18  15 11 17 13 14 a)  b)  c)  d)  6  1  5 24 21  12 18 10 25
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... Bài 9: Tính: 5  1 3 2 1  1 2  3  a)  b)  c)  d)  7 3 8 5 16 15 5 4
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 10: Tính: (số nguyên với phân số) 3 1 1 1 a) 1 b) 1 c)  2 d) 5  4 2 5 6
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... Bài 11: Tính: 2 2 2 5 a) 3  b) 3  c) 3  d) 4  7 5 3 7
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 18
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... Bài 12: Tính:  4   5  3  3  a) 2    b) ( 2  )  c)  3 d) 6      5  8 4   20 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 13: Tính hợp lí: 5 5 2 2 5  12 13 2 2  3 3  13 a)    b)    c)    12 3 12 3 8 7 8 7 5 8 5 8
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 14: Tính hợp lí: 2 3  7  3 5 4  11  2 1  a)   b)   c)   9 10 10 7 13 7 6 5 6
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 19
FB: Nguyễn Văn Thanh, Toán 9, 10, 11, 12 KV Cây Xăng 26, TP. Biên Hòa –ĐT(Zalo).(0918)389.908
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 15: Tính hợp lí: 5  4   5   6   6   7   a)   2   b)  1   c)  1   9  9  11  11  13  13 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
Bài 16: Tính hợp lí:  3 2   1   2  5   4 14  1  19  a)     b)     c)      5 7  5  5  6   5 13  13 20 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
......................................................................................................................................................................... Bài 17: Tính hợp lí: 2   47 5  2  4  7  1  7  5  13  a)     b)     c)     49  49 3   17  17 16  1  8  12 1  8 
.........................................................................................................................................................................
.........................................................................................................................................................................
.........................................................................................................................................................................
FanPage: Thầy Thanh chuyên Toán. Toán Học Trẻ Hàm Rồng – Biên Hòa 20