Số phức và các phép toán về số phức – Diệp Tuân Toán 12

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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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4
SỐ PHỨC
A-L THUY󰈸T
I. Định nghĩa.
Mỗi biểu thức có dạng
a bi
với
được gọi là số phức.
Trong đó:
Gọi
a
là phần thực,
b
là phần ảo của số phức
.z
S
i
2
1i 
được gi là đơn v o.
Tập số phức
z a bi
được kí hiệu
2
{ | , ; 1}.a bi a b i
Tập số thực
.
dụ 1. Số phức
32zi
có phần thực là ….. phần ảo là
.....
Đặc biệt:
Khi phn o
0b z a z
là s thc.
Khi phần thực
0a z bi z
là số thuần ảo.
Số
0 0 0i
vừa là số thực, vừa là số ảo.
II. Hai s phc bng nhau.
Hai s phc là bng nhau nếu phn thc và phn o của chúng tương ứng bng nhau.
Tc là
ac
a bi c di
bd
vi
, , , .a b c d
dụ 2.
a). Tìm các số thực
, ,xy
biết rằng
(2 1) (3 2) ( 2) ( 4) .x y i x y i
b). Tìm các số thực
, ,xy
sao cho
'zz
biết
3 9 3 , ' 12 5 7 ;z x i z y i
c). Tìm các số thực
, ,xy
biết
23
2
( 2 ) 3 1 1 26 14 .x y i i y x i i
Lời giải
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III. Biểu diễn hình học của số phức
Đim
( ; )M a b
trong h trc tọa độ vuông góc ca mt phẳng được gọi điểm biu din ca s
phc
.z a bi
dụ 3.
Quan sát hình vẽ bên cạnh, ta có:
Điểm
A
biểu diễn cho số phức: ………………
Điểm
B
biểu diễn cho số phức: ………………
Điểm
C
biểu diễn cho số phức: ………………
Điểm
D
biểu diễn cho số phức: ………………
§BI 1. KHÁI NIM S PHC
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dụ 4. Trong mặt phẳng phức, gọi
A
,
B
,
C
,
D
lần lượt là các điểm biểu diễn số phức của
1
1zi
,
2
12zi
,
3
2zi
,
4
3zi
. Gọi
S
là diện tích tứ giác
ABCD
. Tính
S
.
Lời giải
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IV. đun của số phức
Gi s s phc
z a bi
đưc biu din bởi điểm
( ; )M a b
trên
mt phng tọa độ.
Độ dài của véctơ
OM
đưc gọi là môđun của s phc
z
đưc kí hiu là
.z
Khi đó:
22
.z OM a bi a b
Kết qu:
z
ta có:
2
2
0, 0 0, z z z z z
1 2 1 2
. . ,z z z z
2
.,z z z
,zz
1
1
22
z
z
zz

dụ 5. Tìm môđun của các số phức sau:
1 3zi
32zi
Lời giải
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V. Số phức liên hợp
1. Định nghĩa. Cho s phc
, ( , ).z a bi a b
Ta gi
a bi
là s phc liên hp ca
z
và được kí hiu là
.z a bi
- b
b
a
O
y
x
z
= a - bi
z = a + bi
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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dụ 6. Cho các số phức sau
12
3 2 , 4 3 .z i z i
Hãy tìm số phức liên hợp của số phức đó.
Lời giải
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2. Tính cht.
Trên mặt phẳng tọa độ, các điểm biểu diễn
z
z
đối xứng với nhau qua trục
.Ox
Từ định nghĩa, ta có các kết quả sau:
;zz
.zz
1 2 1 2
.z z z z
1 2 1 2
. . .z z z z
11
22
zz
zz




z
là số thực
.zz
z
là s thun o
.zz
dụ 7. Cho
2 1 3 5 , ,z a b i a b
. Tìm các s
,ab
để
a).
z
là s thc b).
z
là s o.
Lời giải
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dụ 8. Tìm
mR
để s phc
2
1 1 1z mi mi
là s thun o.
Lời giải
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VI. Cộng, trừ, nhân, chia số phức.
Cho hai số phức
1
z a bi
2
.z c di
1. Phép cộng phép trừ hai số phức được thực hiện theo quy tắc cộng, trừ đa thức.
Phép cộng:
12
( ) ) ( ) ( ) .(z z a bi c di a c b d i
Phép trừ:
12
( ) ) ( ) ( ) .(z z a bi c di a c b d i
2. Số phức đối của số phức
z a bi
.z a bi
Do đó
( ) ( ) 0.z z z z
dụ 9. Cho hai số phức
1
52zi
2
3 7 .zi
Tìm phần thực, phần ảo môđun của số
phức
12
w z z
và số phức
21
w z z

Lời giải
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3. Phép nhân số phức được thực hiện theo quy tắc nhân đa thức, rồi thay
2
1i 
trong kết quả nhận
được. Cụ thể
12
. ( ) ( ) .z z ab bd ad bc i
dụ 10. Cho hai số phức:
1
52zi
2
4 3 .zi
Hãy tính:
12
.,zz
1
2
,
z
z
12
.zz
Lời giải
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4. Phép chia:
1 1 2 1 2
2
2
2 2 2 2
2
22
2
..
, ( 0).
.
z z z z z
ac bd bc ad
iz
z c d c d
zz
z


5. Số phức nghịch đảo của
0z a bi
2
22
1 zz
z a b
z
dụ 11. Tìm phần thực, phần ảo và môđun của số phức sau:
23z i i i
1). 2).
34
4
i
z
i
3).
2
1 1 8 1 2i i z i i z
Li gii.
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dụ 12. Tìm nghịch đo ca s phc sau:
a).
3 4 ;zi
b).
3 2 ;zi
c).
15
;
32
i
z
i
d).
2
3 2 .zi
Li gii.
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Nhn t: Quá trình thc hin trên, thực ra ta đang dùng công thức sau:
2
2
1
.
z
z z z
z
z
VII. Lũy tha đơn v o
.
n
i
Ta có:
0 1 2 3 2
1, , 1, ,i i i i i i i i
bằng quy nạp ta có
1 khi 4
khi 4 1
1 khi 4 2
khi 4 3
n
nk
i n k
i
nk
i n k

Do đó:
*
{ 1;1; ; },
n
i i i n
dụ 13. Tính
7
7
11
2
Ai
ii




,
2015
1
,
1
i
B
i



2026
17
,
43
i
C
i



6
5
1
.
22
i
D
i
Li gii.
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B. PHÂN DẠNG I TẬP MINH HỌA
DẠNG 1. C PHÉP TOÁN VỀ SỐ PHỨC M THUỘC TÍNH CỦA NÓ.
Nhóm bài toán 1. Tính toán cộng trừ, nhân chia c số phức
1. Phương pháp.
Áp dng các công thc cng, trừ, nhân, chia và lũy thừa s phc.
S phc và thuc tính ca nó.
Tìm phn thc và phn o:
z a bi
, suy ra phn thc
a
, phn o
b
Biu din hình hc ca s phc:
Lũy thừa đơn vị o:
1 khi 4
khi 4 1
1 khi 4 2
khi 4 3
n
nk
i n k
i
nk
i n k

2. Bài tập minh họa.
Bài tp 1. Thc hin các phép tính sau:
a).
1
1 4 3
A
ii

. b).
56
43
i
B
i

. c).
1
13
22
C
i
.
d)
32i
D
i
. e).
2026
17
43
i
E
i



f).
100 98 96
3 1 4 1 4 1 .F i i i i
Li gii
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Bài tp 2. Viết các s phức sau đây dưới dng
, , :a bi a b R
a).
33
2 1 2 3 2 ;z i i i i
b).
1 3 1 2
;
1 2 1
i i i
z
i i i
c).
2
21
;
2 1 3 1
ii
z
ii

d).
5
3
2
12
i
z
i
Li gii
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3. Câu hỏi trắc nghiệm.
Mức độ 1. Nhận biết
u 1.ng Thành Nam) S phc
,z a bi a b
là s thun o khi và ch khi
A.
0a
,
0b
B.
0a
,
0b
C.
0a
D.
0b
Li gii
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u 2.(Đặng Thành Nam) Với mọi số phức
z
. Mệnh đề nào sau đây sai ?
A.
z
là một số thực. B.
z
là một số phức.
C.
z
là một số thực dương. D.
z
là một số thực không âm.
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u 3.(THPT Kim Liên 2017)Mệnh đề nào dưới đây là đúng?
A.
,z z z
luôn là số thực. B.
,
z
z
z

luôn là số thực.
C.
,z z z
luôn là số thuần ảo. D.
,.z z z
luôn là số thực không âm.
Li gii
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u 4.(S GD và Đào Tạo Hưng Yên) Trên mt phng tọa độ, tìm tp hợp điểm biu din s phc
z
sao cho
2
z
là s thun o.
A. Hai đường thng
yx
yx
. B. Trc
Ox
.
C. Hai đường thng
yx
yx
, b đi điểm
0;0O
. D. Trc
Oy
.
Li gii
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u 5.(THPT Ngô Quyền Hà Nội 2019) Tìm mệnh đề sai trong các mệnh đề sau:
A. Số phức
z a bi
có môđun là
22
.ab
B. Số phức
z a bi
có số phức đối
z a bi

.
C. Số phức
0z a bi
khi và chỉ khi
0
0
a
b
.
D. Số phức
z a bi
được biểu diễn bởi điểm
;M a b
trong mặt phẳng phức
Oxy
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 6.(THPT Kim Liên 2017) Cho hai số phức
z a bi
, ( , , , ), 0z a b i a b a b z
.
Khẳng định nào sau đây là đúng?
A.
22
( )( - i)z a bi a b
z a b

. B.
22
( )( i)
'
z a bi a b
z a b


.
C.
22
( )( i)z a bi a b
z a b


. D.
22
( )( i)z a bi a b
z a b


.
Li gii
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u 7.(Sở GD ĐT Quảng Nam 2019) Số phức liên hợp của số phức
23zi
A.
32zi
. B.
32zi
. C.
23zi
. D.
23zi
.
Li gii
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u 8.(S GD ĐT Đà Nng 2019) Phn o ca s phc
76zi
bng.
A.
6
. B.
6i
. C.
6
. D.
6i
.
Li gii
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u 9.(Chuyên Đại Hc Phm Ni) Môđun của s phc
52zi
bng
A.
29
. B.
3
. C.
7
. D.
29
.
Li gii
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u 10.(Chuyên Quý Đôn Qung Tr) Cho s phc
2
12zi
. Tính mô đun của s phc
1
z
.
A.
1
5
. B.
5
. C.
1
25
. D.
1
5
.
Li gii
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u 11.(THPT Thăng Long 2019) Cho số phức
z
phần thực bằng
2
và phần ảo bằng
3
.
Môđun của số phức
3 iz
A.
2 10
. B.
10
. C.
22
. D.
2
.
Li gii
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
u 12.(THPT Kim Liên 2017) Cho số phức
57zi
. Hãy xác định phần thực và phần ảo của số
phức
z
.
A. Phần thực bằng 5 và phần ảo bằng
7i
.
B. Phần thực bằng 5 và phần ảo bằng
7
.
C. Phần thực bằng 5 và phần ảo bằng 7.
D. Phần thực bằng 5 và phần ảo bằng
7i
.
Li gii
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u 13.(THPT Cm Giàng) Cho s phc
34zi
. Tìm phn thc và phn o ca s phc
z
.
A. Phn thc là
4
và phn o là
3i
. B. Phn thc là
3
và phn o là
4
.
C. Phn thc là
4
và phn o là
3
. D. Phn thc là
3
và phn o là
4i
.
Li gii
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u 14.(THPT Yên Dũng 2019) Cho số phức
z
số phức liên hợp
32zi
. Tổng phần thực
phần ảo của số phức
z
bằng
A.
5
. B.
1
. C.
5
. D.
1
.
Li gii
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u 15.(THPT Chuyên Bc Giang 2019) Cho s phc
12zi
. Tìm tng phn thc và phn o ca
s phc
2w z z
.
A. 3. B. 5. C. 1. D. 2.
Li gii
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u 16.(S GD ĐT Kiên Giang 2019) Cho hai số phức
1
13zi
2
34zi
.
Môđun của số phức
1
2
z
z
w
A.
10
2
w
. B.
9 13
25 25
i
w
. C.
5
10
w
. D.
10
5
w
.
Li gii
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u 17.(THPT Kim Liên 2019) Cho hai s phc
1
23zi
;
2
1zi
. Tính
12
3zz
.
A.
12
3 11zz
. B.
12
3 11zz
. C.
12
3 61zz
. D.
12
3 61zz
.
Lời giải
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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u 18.(S GD ĐT KonTum ) Cho s phc
z
tha mãn
12
23
12
iz
i
i

.
S phc liên hợp ca
z
z a bi
vi
,ab
. Giá tr ca
ab
bng
A.
1
. B.
12
. C.
6
. D.
1
.
Li gii
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u 19.(THPT Chuyên Nguyễn Huệ 2019) Cho hai số phức
1 2 3 1 2
4 3 , 4 3 , .z i z i z z z
.
Lựa chọn phương án đúng:
A.
3
25z
. B.
2
31
zz
. C.
1 2 1 2
z z z z
. D.
12
zz
.
Li gii
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u 20.(Đặng Thành Nam) Với mọi số thuần ảo
z
, số
2
2
zz
A.
số thực dương. B.
số thực âm. C.
số 0. D.
số thuần ảo khác 0.
Li gii
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u 21.( THPT Kim Liên 2017)Cho hai số phức
2z a i
,
a
5zi

.
Tìm điều kin ca
a
để
zz
là mt s thc
A.
2
5
a 
. B.
2
5
a 
. C.
10a
. D.
10a
.
Li gii
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u 22.(THPT Thanh Chương 2019) S phc
z
thỏa mãn đẳng thc
1 1 3i z i
A.
12zi
. B.
12zi
. C.
33zi
. D.
33zi
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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u 23.(S GD và ĐT Đà Nng 2019) Cho hai s phc
1
1zi
2
1zi
.
Giá tr ca biu thc
12
z iz
bng
A.
22i
. B.
2i
. C.
2
. D.
22i
.
Li gii
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u 24.(THPT Chuyên Đắc Lắc 2019) Cho số phức thỏa mãn . Tổng phần thực
và phần ảo của bằng
A. . B. . C. . D.
Li gii
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u 25.(THPT Nguyn Du Dak-Lak 2019) Môđun của s phc
3
5 3 1z i i
A.
25
. B.
35
. C.
53
. D.
52
.
Li gii
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u 26.(THPT Chuyên Lam Sơn 2019) Cho hai số phức
1
12zi
2
34zi
.
Số phức
1 2 1 2
23z z z z
là số phức nào sau đây?
A.
10i
. B.
10i
. C.
11 8i
. D.
11 10i
.
Li gii
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Mức độ 2. Thông Hiểu
u 27.(THPT C Loa 2019) Cho hai s phc
1
2zi
,
2
13zi
.
Tính mô-đun của s phc
2
12
w z z
.
A.
7w
. B.
5w
. C.
19w
. D.
53w
.
Li gii
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z
1 14 2i z i
z
14
2
2
14
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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u 28.(THPT Nam Tiền Hải 2019) Cho số phức
2
1 1 2 .z i i
Số phức
z
có phần ảo là
A.
2i
. B.
4
. C.
2
. D.
4
.
Li gii
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u 29.(THPT Chuyên Quý Đôn Qung Tr) Cho s phc
2 3 4
32
ii
z
i

. Tìm tọa độ đim
biu din ca s phc
z
trên mt phng
Oxy
.
A.
1;4
. B.
1;4
. C.
1; 4
. D.
1; 4
.
Li gii
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u 30.(THPT Chuyên Bc Giang 2019) Cho s phc
z
tha mãn
2
3 2 2 4i z i i
.
Tìm tọa độ đim
M
biu din s phc
z
.
A.
1;1M
. B.
1; 1M 
. C.
1;1M
. D.
1; 1M
.
Li gii
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u 31.(Trường Thực Hành Cao Nguyên 2019) Cho
i
là đơn vị ảo. Nghiệm của phương trình
2
31
2
i
zi
i
A.
23
.
15 5
i
B.
23
.
15 5
i
C.
22
.
15 5
i
D.
23
.
15 5
i
Li gii
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u 32.(THPT Pc Trch Tĩnh 2019) Tính môđun của số phức
z
, biết:
1 2 2 12 .i z i i
A.
5
. B.
7
. C.
1
2
. D.
2 2.
Li gii
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u 33.(THPT Chuyên Hunh Mn Đạt 2019)
Cho s phc
3 2 .zi
Tìm phn o ca s phc
12w i z
.
A.
4
. B. 7. C. 4. D. 4
i
.
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u 34.(THPT Kim Liên 2019) Cho s phc
22
2 1 3z i i
. Tng phn thc phn o ca
z
A. 1. B.
1
. C.
21
. D.
21
.
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u 35.(S GD Và Đào Tạo Cần Thơ 2019) Phn o ca s phc
3
5 2 (1 )z i i
bng:
A.
0
. B.
7
. C.
7
. D.
7
.
Li gii
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u 36. (THPT Nông Cng 2019) Cho các s phc
1
12zi
,
2
z 2 3i
. S phc nào sau
phn o lớn hơn.
A.
21
zz
. B.
1
z
. C.
2
.z
D.
21
zz
.
Li gii
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u 37.(THPT Gia Lc Hi Dương 2019) Tìm tọa độ đim
M
điểm biu din s phc
z
biết
z
thỏa mãn phương trình
1 3 5i z i
.
A.
1;4M
. B.
1; 4M 
. C.
1;4M
. D.
1; 4M
.
Li gii
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u 38.(THPT Chuyên KHTN 2019) Cho số phức
12zi
. Môđun của số phức
iz z
bằng
A.
6
. B.
2
. C.
32
. D.
18
.
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 39.(THPT ISCHOOL Nha Trang) Cho s phc
2z a bi
,ab
. Khi đó phần thc ca s
phc
23w z i i
bng
A.
6 2 1ab
. B.
2 12 3ab
. C.
6 4 1ab
. D.
2 6 3ab
.
Li gii
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u 40.(Lương Thế Vinh Đồng Nai)
Cho số phức
z
thỏa mãn
Mệnh đề nào sau đây đúng?
A.
13 4
55
zi
. B.
13 4
55
zi
. C.
13 4
55
zi
. D.
13 4
55
zi
.
Li gii
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u 41.(THPT Thanh Chương 2019) Cho s phc
z
tha mãn
3
13
1
i
z
i
.
đun của s phc
.w z i z
bng
A.
11
. B.
8
.
C.
82
. D.
0
.
Lời giải
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u 42.(THPT Chuyên Hoàng Văn Thụ 2019) Cho s phc
z a bi
,
,ab
thỏa mãn điều kin
1 1 2 2 i z i i
. Giá tr ca
.ab
bng
A.
2
. B.
2
. C.
1
. D.
1
.
Lời giải
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u 43.(THPT Chuyên Hà Nội 2019) Cho số phức z thỏa mãn điều kiện
(1 )( ) 2 2i z i z i
.
Mô đun của số phức
2
21zz
w
z

là:
A.
22
. B.
5
. C.
10
. D.
25
.
Lời giải
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 44.(THPT Chuyên H Long 2018) Cho s phc
z
tha
1 2 1 5 1i i z i i i
.
Tính môđun của s phc
2
12w z z
.
A.
100
. B.
10
. C.
5
. D.
10
.
Lời giải
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u 45.(Sở GD và ĐT Nam Định 2019) Cho số phức
,z a bi a b
thỏa
13
1
12
i
a b i
i
. Giá trị nào dưới đây là môđun của
z
?
A.
5
. B.
1
. C.
10
. D.
5
.
Lời giải
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u 46.(THPT Gia Lc 2019)Cho số phức
z
thỏa mãn
2
3 2 2 4i z i i
.
Tìm hiệu phần thực và phần ảo của số phức
z
.
A.
3
. B.
2
. C.
1
. D.
0
.
Lời giải
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Mức độ 3. Vận dụng
u 47.(S GD và ĐT Ninh Bình 2019)
Tính tng phn thc ca tt c các s phc
0z
tha mãn
.
A.
2
. B.
2
. C.
3
. D.
3
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
17
Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 48.(S GD và ĐT KonTum 2019) Cho s phc
z
tha mãn
2
23
34
2
iz
i
i
z
z
.
Giá tr ca
z
bng
A.
5
. B.
10
. C.
1
. D.
2
.
Lời giải
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Nhóm bài toán 2. Hai số phức bằng nhau
1. Phương pháp.
Áp dng các công thc cng, tr, nhân, chia s phức để rút gọn đưa về nh cht hai s phc
bng nhau.
ac
a bi c di
bd
với
, , , .a b c d
2. Bài tập minh họa.
Bài tp 3. Tìm các số thực
x
y
thỏa các điều kiện sau
2 1 (1 2 ) 2(2 ) .x y i i yi x
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Bài tp 4. Tìm các số thực
x
y
thỏa các điều kiện sau là:
a).
2 1 1 2 2 3 2x y i x y i
b).
4 3 3 2 1 3x y i y x i
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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c).
3
3 5 1 2 7 32x i y i i
d).
11
11
xy
ii


Li gii
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e).
1
23
33
y
i
x i i

f).
1 3 2 1 4x i yi i x i
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Lời giải
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Bài tp 5. Tìm các s thc
,xy
sao cho
'zz
, vi từng trường hp
a).
23
2
( 2 ) 3 1 1 26 14 .x y i i y x i i
b).
9
6
2 2 2
4
3
2 3 1 2 320 896
1
i
x y i i y x i
i
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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3. Câu hỏi trắc nghiệm.
Mức độ 1. Nhận biết
u 49.(THPT Chuyên n La 2019)
Tìm các s thc
x
y
tha mãn
3 2 2 1 1 5x y i x y i
, vi
i
là đơn vị o.
A.
3
,2
2
xy
. B.
34
,
23
xy
. C.
4
1,
3
xy
. D.
34
,
23
xy
.
Li gii
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u 50.ng Thành Nam) Tìm các s thc
a
b
tha
2 1 2a b i i i
vi
i
là đơn vị o.
A.
0, 2ab
. B.
1
,1
2
ab
. C.
0, 1ab
. D.
1, 2ab
.
Li gii
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 51.(THPT Kim Liên 2017)
Tìm các số thực
x
y
thỏa mãn điều kiện
2 1 3 2 2 4x y i x y i
A.
1
3
x
y

. B.
1
3
x
y

. C.
1
3
x
y


. D.
1
3
x
y
.
Li gii
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u 52.(S GD Và ĐT Thanh Hóa 2019)
Biết rằng có duy nhất 1 cặp số thực
;xy
thỏa mãn
53x y x y i i
. Tính
2S x y
.
A.
5S
. B.
4S
. C.
6S
. D.
3S
.
Li gii
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u 53.(Đặng Thành Nam 2019) Tìm các số thực
a
b
thoả mãn
( ) 1 3a b i i i
với
i
đơn
vị ảo.
A.
2, 3ab
. B.
0, 3ab
. C.
1, 3ab
. D.
2, 4ab
.
Li gii
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u 54.(Sở GD & ĐT Cà Mau 2019) Tìm các s thc
a
b
tha mãn
4 2 1 6ai bi i i
vi
i
đơn vị o.
A.
1
,6
4
ab
. B.
1
,6
4
ab
. C.
1, 1ab
. D.
1, 1ab
.
Li gii
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u 55.(THPT Qúy Đôn 2019) Tìm các s thc
x
,
y
tha mãn
2 1 2 1x y i i
vi
i
đơn vị o.
A.
1; 1xy
. B.
1; 2xy
. C.
1; 3xy
. D.
1; 3xy
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
u 56.(THPT Chuyên Thái Nguyên 2019) Cho các số thực
x
,
y
thỏa mãn
4 3 2 4 2i x yi
.
Tính giá trị của
P x y
.
A.
4P
. B.
7P
. C.
1P 
. D.
8P
.
Li gii
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u 57.(THPT Sơn Tây Hà Nội 2019) Các số thực
x
,
y
thỏa
3 5 1 2 9 16x i y i i
trong đó
2
1i 
. Giá trị của biểu thức
T x y
A.
3
. B.
5
. C.
0
. D.
1
.
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u 58.(THPT TX Quãng Tr 2019) Cho hai s thc
,xy
tha mãn
3 2 1 4 1 24x i y i i
.
Giá tr
xy
bng
A.
3
. B.
2
. C.
4
. D.
3
.
Lời giải
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u 59.(THPT NguynCông Tr Tĩnh 2019)
Các s thc
x
,
y
tha mãn
3 5 2 1x y xi y x y i
, vi
i
là đơn vị o là.
A.
14
;
77
xy
. B.
24
;
77
xy
. C.
14
;
77
xy
. D.
14
;
77
xy
Lời giải
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Mức độ 2. Thông Hiểu
u 60.(THPT Kim Liên 2019)
Tìm các s thc
,xy
tha mãn
3 2 4 1 2 i x yi i i x yi
A.
3, 1 xy
. B.
3, 1 xy
. C.
1, 3 xy
. D.
3, 1xy
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 61.(Đặng Thành Nam 2019) Tìm tt c các s thc
,xy
để hai s phc
25
1
9 4 10z y xi
2 11
2
8 20z y i
là hai s phc liên hp ca nhau.
A.
2
2
x
y

. B.
2
2
x
y

. C.
2
2
x
y


. D.
2
2
x
y

.
Li gii
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u 62.(THPT Cm Giàng 2019) Tìm hai s thc
x
y
tha mãn
2 3 1 3 1 6x yi i i
vi
i
là đơn vị o.
` A.
1x
;
3y 
. B.
1x 
;
3y 
. C.
1x 
;
1y 
. D.
1x
;
1y 
.
Lời giải
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u 63.(S GD và ĐT Bình Thuận 2019) Nếu hai số thực
,xy
thỏa
3 2 1 4 1 24x i y i i
thì
xy
bằng?
A.
3
. B.
3
. C.
7
. D.
7
Lời giải
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u 64.(Tn Hc Tui Tr 2019) Cho cp s
;xy
tha mãn:
2 1 2 3 7x y i y i i
.
Khi đó biểu thc
2
P x xy
nhn giá tr nào sau đây:
A.
30
. B.
40
. C.
10
. D.
20
.
Lời giải
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u 65.(Toán Hc Tui tr) Cho cp s
;xy
tha mãn:
2 3 1 2 5 4i x y i i
.
Khi đó biểu thc
2
2P x y
nhn giá tr nào sau đây:
A.
3
. B.
4
. C.
1
. D.
2
.
Lời giải
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Mức độ 3. Vận dụng
u 66.(THPT Q Đôn Điện Biên 2019)
Tìm hai s thc
x
và
y
tha mãn
3 2 3 4 3x yi i x i
vi
i
là đơn vị o.
A.
3;x
1y 
. B.
2
;
3
x
1y 
. C.
3;x
3y 
. D.
3;x 
1y 
.
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u 67.ng Thành Nam 2019) S thc
x
y
tho mãn
22
(2 4 ) 4 29 0x xy y i x y
vi
i
là đơn vị o là
A.
5
0
x
y
. B.
2
5
x
y


. C.
2
5
x
y

. D.
0
29
x
y

.
Li gii
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u 68.(THPT Kim Liên 2018) Tìm các s thc
x
,
y
tha mãn
1 3 2 1 2 3 6i x y y i i
.
A.
5x 
;
4y 
. B.
5x
;
4y
. C.
5x
;
4y 
. D.
5x 
;
4y
.
Li gii
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u 69.(Đề Chính Thức 2018 ) Tìm hai số thực
x
y
thỏa mãn
3 2 2 2 3x yi i x i
với
i
là đơn vị ảo.
A.
2; 2xy
. B.
2; 1xy
. C.
2; 2xy
. D.
2; 1xy
.
Li gii
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 70.(Đề Chính Thức 2018) Tìm hai số thực
x
y
thỏa mãn
3 4 2 5 2x yi i x i
với
i
là đơn vị ảo.
A.
2x 
;
4y
. B.
2x
;
4y
. C.
2x 
;
0y
. D.
2x
;
0y
.
Li gii
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u 71.(Đề Thử Nghiệm 2018) Cho số phức
,z a bi a b
thỏa mãn
22
2
2 1 2
iz z i
z
ii



1z
. Tính
22
P a b ab
.
A.
0P
. B.
1P
. C.
29
100
P
. D.
5P
.
Li gii
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Nhóm bài toán 3. Tính toán số phức chứa lũy thừa đơn vị ảo
n
i
.
1. Phương pháp.
Áp dng các công thc lũy thừa đơn vị o:
1 khi 4
khi 4 1
1 khi 4 2
khi 4 3
n
nk
i n k
i
nk
i n k

Áp dng các phép toán cng tr, nhân chai s phc.
2. Bài tập minh họa.
Bài tp 6. Tính các s phc sau:
a).
5
4 5 4 3ii


b).
2006
1 i
Li gii
……………………………………………………………………
……………………………………………………………………
……………………………………………………………………
Lời giải
…………………………………………………………………
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
c).
3
23i
d).
2019
1 i
Li gii
……………………………………………………………………
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Lời giải
…………………………………………………………………
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Bài tp 7. Tìm phần thực, phần ảo và môđun của
10
11
78
.
87
i
z
i
Li gii
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Bài tp 8. Tính
33
10
11
1 2 3 2 3 ;
1
i
B i i i
ii



Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Bài tp 9. Tính
2 3 2012
1 ... .S i i i i
Li gii
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Bài tp 10. Tính
2 3 20
1 1 1 1 ... 1C i i i i
Li gii
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Bài tp 11. Tính tng
2 3 2012
2 3 ... 2012. .S i i i i
Li gii
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3. Câu hỏi trắc nghiệm.
Mức độ 1. Nhận biết
u 72.(THPT Kim Liên 2017)
Cho
i
là đơn vị ảo,
n
là số nguyên dương. Mệnh đề nào sau đây đúng?
A.
1
0
nn
ii

. B.
2
0
nn
ii

. C.
2
0
nn
ii

. D.
1
0
nn
ii

.
Li gii
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u 73.(Sở GDĐT Lâm Đồng 2017) Phần thực của số phức
30
(1 )i
bằng.
A.
1
. B.
15
2
. C.
15
2
. D.
0
.
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Li gii
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u 74.(THPT Yên Ninh Bình 2019) Cho hai s thc
,xy
tha mãn
2019
3 5 9 14x i y i i
.
Giá tr ca
xy
A.
1
. B.
4
. C.
2
. D.
3
.
Li gii
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u 75.(THPT Nguyn Hu 2019) Tính môđun của số phức
2016
1zi
.
A.
1008
2
. B.
1008
2
. C.
2016
2
. D.
1000
2
.
Li gii
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u 76.(THPT Chuyên Nguyn Du 2019) Mô đun của s phc
6
5 2 1ii
bng
A.
55
. B.
53
. C.
33
. D.
35
.
Li gii
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u 77.(THTT S 2-485 2018) Trong các s phc:
3
1 i
,
4
1 i
,
5
1 i
,
6
1 i
s phc nào
s phc thun o?
A.
3
1 i
. B.
4
1 i
. C.
5
1 i
. D.
6
1 i
.
Li gii
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u 78.(Chuyên Đại Học Vinh 2017)Cho số phức
z
thỏa mãn:
3
13
1
i
z
i
.
Tìm môđun của
z iz
.
A.
42
. B.
4
. C.
82
. D.
8
.
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
Li gii
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Mức độ 2. Thông Hiểu
u 79.(THPT Thun Thành 2019) Cho s phc
5
1
1
i
z
i



. Tính
5 6 7 8
z z z z
.
A.
2
. B.
0
. C.
4i
. D.
4
.
Li gii
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u 80.(Chuyên ĐH Vinh 2019) Cho s phc tha mãn . Mô đun của bng
A. 5 B. C. D.
Li gii
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u 81.(THPT Quế Võ 2019) Biểu diễn về dạng
z a bi
của số phức
2016
2
12
i
z
i
là số phức nào?
A.
34
25 25
i
. B.
34
25 25
i
. C.
34
25 25
i
. D.
34
25 25
i
.
Li gii
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u 82.(PTNK-ĐHQG TP HCM 2018) Tính
2018 2018
1 3 1 3P i i
.
A.
2P
. B.
1010
2P
. C.
2019
2P
. D.
4P
.
Li gii
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z
2019
1
34
1
i
z i i
i




z
1
5
2
5
5
2
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 83. Tính giá trị của biểu thức
2024
.
1
i
P
i



A.
2024
1
2
P 
. B.
1012
1
2
P
. C.
2024
1
2
P
. D.
1012
1
2
P 
.
Li gii
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u 84. Cho số phức
2017
1
1
i
z
i



. Tính
7 15
..P z z z
.
A.
.Pi
B.
1P
. C.
Pi
. D.
1P 
.
Li gii
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u 85. Cho số phức
5
1
1
i
z
i



. Tính
5 6 7 8
.S z z z z
A.
0S
. B.
1S
. C.
3S
. D.
4S
.
Li gii
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u 86. Tìm phần ảo
b
của số phức
16 8
11
11
ii
z
ii



.
A.
1b 
. B.
2b
. C.
1b
. D.
0b
.
Li gii
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u 87.(THPT Chuyên Hồng Phong 2019) Cho
2 4 6 2016 2018
1 i i i i i a bi
với
,ab
.
Tính giá trị của
3H a b
.
A.
0H
. B.
3H
. C.
2
. D.
3030H
.
Li gii
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u 88.(S GD V ĐT Đồng Tháp 2018) Tính tng
3 6 2016
1 ...S i i i
.
A.
1S
. B.
Si
. C.
Si
. D.
1S 
.
Li gii
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u 89.(TTGDTX Nha Trang 2019) Cho
2017
1zi
. Tìm
z
.
A.
1008 1008
2 2 zi
. B.
1008 1008
2zi
. C.
1008 1008
2 2 zi
.
D.
1008 1008
2zi
.
Li gii
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u 90.(THPT Nguyn Th Minh Khai) S phc
2 20
1 (1 ) (1 ) ... (1 )i i i
có giá tr bng.
A.
10
2
. B.
10 10
22i
. C.
10 10
2 (2 1)i
. D.
10 10
2 (2 1)i
.
Li gii
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u 91.(THPT chuyên Quc Hc 2019) Cho số phức
2 3 20
1 1 1 1 ... 1w i i i i
.
Tìm phần thực và phần ảo của số phức
w
.
A. Phần thực bằng
10
2
và phần ảo bằng
10
12
.
B. Phần thực bằng
10
2
và phần ảo bằng
10
12
.
C. Phần thực bằng
10
2
và phần ảo bằng
10
12
.
D. Phần thực bằng
10
2
và phần ảo bằng
10
12
.
Li gii
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 92.(Cụm 4 Hồ Chí Minh 2019) Cho hai số phức
1
2zi
,
2
12zi
.
Tìm môđun của số phức
2016
1
2017
2
z
w
z
.
A.
3w
. B.
5w
. C.
1
5
w
. D.
3w
.
Li gii
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Mức độ 3. Vận dụng
u 93. Cho số phức
z
thỏa mãn
8
2
1
i
iz
i



. Gọi
, ab
lần lượt là phần thực và phần ảo của số
phức
2w i z
. Tính
.S a b
A.
16S 
. B.
16S
. C.
32S
. D.
48S
.
Li gii
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u 94. bao nhiêu số nguyên
n
sao cho
4
ni
là một số nguyên?
A.
2.
B.
3.
C.
4.
D. Vô số.
Li gii
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 95. Có bao nhiêu giá trị
m
nguyên dương thuộc đoạn
1;50
để
26
3
m
i
z
i



là số thuần ảo?
A.
24.
B.
25.
C.
26.
D.
50
.
Li gii
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u 96. Cho số phức
z
thỏa mãn
2 1 2 3 2z i i z i
. Tìm phần thực
a
của số phức
9
z
A.
1a
. B.
16a
. C.
1a 
. D.
16a 
.
Li gii
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Câu 97. Cho s phức
z
tha mãn
2015
2 3 1 1z i i i
. Tìm phn o
b
của số phc
23w z i
A.
2015
2b
. B.
1007
2b
. C.
0b
. D.
1007
2b 
.
Li gii
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u 98. Cho số phức tùy ý
1z
.
Xét các số phức
2017
2
2
1
ii
zz
z
3
2
1
zz
zz
z
. Khi đó:
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
33
Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
A.
là số thực,
là số thực. B.
là số thực,
là số ảo.
C.
là số ảo,
là số ảo. D.
là số ảo,
là số thực.
Li gii
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u 99.(THPT Thường Kit 2019) Cho s phc
,z a bi a b
tha mãn
2 3 3z iz i
.
Tính giá tr biu thc:
2019 2019
.P a i b i
A.
1010
2
. B.
1009
2
. C.
1011
2
. D.
1008
2
.
Li gii
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u 100.(THPT Kinh Môn 2019)
Tìm phần ảo của số phức
z
, biết số phức liên hợp là
2 3 2019
2 1 1 1z i i i i
A.
1010
2
. B.
1010
2
. C.
1010
21
. D.
1010
21
.
Li gii
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
u 101.(THPT Chu Văn An 2018) S phc
2 2018
1 1 ... 1z i i i
có phn o bng
A.
1009
21
. B.
1009
21
. C.
1009
12
. D.
1009
21
.
Li gii
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Mức độ 4. Vận dụng cao
u 102.(THPT Hai Bà Trưng-Huế) Tính
2 3 2017
1009 2 3 ... 2017S i i i i
trên đoạn
2,4 .
A.
1008 1009i
. B.
1009 2017i
. C.
2017 1009i
. D.
2017 1009i
.
Li gii
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u 103.(Toán Hc Tui Tr 2019) Cho số phức
2 3 2017
1 2 3 4 ... 2018z i i i i
có phần thực là
a
và phần ảo là
b
. Tính
ba
.
A.
1
. B.
1
. C.
1010
. D.
2017
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
Nhóm bài toán 4. Tìm phần thực, phần o, số phức liên hợp môđun của
, .zw
1. Phương pháp.
Áp dng phép chia
2
số phức, ta cần nhân thêm số phức liên hợp của mẫu số.
Nếu sử dụng casio, ta chuyển về chế độ
CMPLX
(mode 2)
(i
tương ứng
ENG).
Khi bài toán yêu cầu tìm các thuộc tính của số phức (phần thực, phần ảo, môđun hoặc số phức
liên hợp) mà đề bài cho giả thiết chứa hai thành phần trong ba thành phần
, , z z z
thì ta sẽ
gọi số phức
22
, z a bi z a bi z a b
với
,,ab
rồi sau đó thu gọn và sử dụng
kết quả hai số phức bằng nhau, giải hệ.
2. Bài tập minh họa.
Bài tp 12. Cho
z
thỏa
1
(2 ) 5 .
1
i
i z i
i
Tìm các thuộc tính của
2
1 2 .w z z
Li gii
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Bài tp 13. Cho số phức
z
thỏa mãn
(2 3 ) (1 2 ) 7 .i z i z i
Tìm môđun của
.z
Li gii
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Bài tp 14. Tìm môđun của s phc
,z
biết rng:
a).
1 2 3 8i z i
b).
2
2 1 2z i i
Li gii
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Lời giải
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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c).
3
13
1
i
z
i




d).
2
1 1 2z i z i
4
Li gii
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Lời giải
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Bài tp 15. Tìm phn o ca s phc
z
, biết
2
3 1 2z z i
Li gii.
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Bài tp 16. Tìm số phức
z
thỏa mãn:
1
1
z
zi
3
1
zi
zi
Lời giải.
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1. Câu hỏi trắc nghiệm.
Mức độ 2. Thông hiểu
u 104.(Sở GD và ĐT Đồng Tháp 2019)Số phức liên hợp của số phức
3 2 3 z i i
A.
67zi
. B.
67zi
. C.
97zi
. D.
97zi
.
Li gii
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Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
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u 105.(Sở GD và ĐT Hà Nam 2019)
Cho các số thực
,ab
thỏa mãn
2 5 7 3i a i b a i


, với
i
là đơn vị ảo. Tính
ab
A.
2
. B.
6
. C.
12
. D.
3
.
Li gii
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u 106.(THPT Nguyễn Trung Thiên 2019) Cho số phức
z
thỏa mãn
2 2 5z iz i
. Môđun của
số phức
z
bằng
A.
7z
. B.
5z
. C.
25z
. D.
145
5
z
.
Li gii
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u 107.(THPT Kim Liên 2018) Cho s phc
z a bi
,
,ab
tha
2
34
11
2
i
i z i
i
.
Tính
10 10P a b
.
A.
42P 
. B.
20P
. C.
4P
. D.
2P
.
Li gii
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u 108.(THPT Pc Trch Tĩnh 2019) Cho số phức . Môđun của số phức
A.
370
10
. B.
10
10
. C.
10
. D.
31
10 10
i
.
Li gii
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3
3
i
zi
i

z
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 109.(THPT Nguyễn Đức Cảnh TháiBình) Tìm số phức
z
thỏa mãn
2 3 2z i z
.
A.
2zi
. B.
2zi
. C.
32zi
. D.
3zi
.
Li gii
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u 110.(Cụm THPT Vũng Tàu) Cho số phức
z
thỏa mãn
23z i z
. Tính
z
.
A.
5z
. B.
35
2
z
. C.
5z
. D.
10z
.
Li gii
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u 111.(Chuyên Đi Hc Vinh 2019) Cho s phc
z
tha mãn
2 6 2 . z z i
Đim biu din s phc
z
có tọa độ
A.
2; 2
. B.
2; 2
. C.
2;2
. D.
2;2
.
Li gii
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u 112.(THPT Chuyên H Long 2019) Tìm số phức
z
biết
4 5 27 7z z i
.
A.
37zi
. B.
37zi
. C.
37zi
. D.
37zi
.
Li gii
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Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
u 113.(Chuyên T Trng 2019) Tìm mô đun của s phc
z
, biết
2 3 17 9z i z i
.
A.
26z
. B.
17z
. C.
29z
. D.
5z
.
Li gii
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u 114.(Sở GD và ĐT Vĩnh Phúc 2019) Cho số phức
z
thỏa mãn
2 3 5z i z i
.
Tính môđun của số phức
z
.
A.
13z
. B.
5z
. C.
13z
. D.
5z
.
Li gii
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u 115.(THPT Kim Liên Hà Ni 2019)
Cho s phc
,,z a bi a b
tha mãn
3 4 5 17 11z i z i
. Tính
ab
.
A.
3ab
. B.
6ab
. C.
6ab 
. D.
3ab 
.
Li gii
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u 116.(THPT Thị Quảng Trị 2019) Cho số phức
z a bi
với
,ab
thỏa
3z i z i
.
Giá trị của
ab
bằng
A.
1
. B.
7
. C.
5
. D.
12
.
Li gii
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 117.(THPT Đoàn Thượng 2019) Gi
1
z
2
z
lần lượt là hai nghim của phương trình
2
4 5 0zz
. Cho s phc
12
11w z z
. Tìm s phc liên hp ca s phc
w
A.
10w 
. B.
5w 
. C.
10w
. D.
4w 
.
Li gii
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u 118.(THPT Chuyên Đại Học Sư Phạm 2019)
Nếu
z a bi
,ab
có s phc nghịch đảo
1
4
a bi
z
thì
A.
22
2ab
. B.
22
4ab
. C.
22
8ab
. D.
22
16ab
.
Li gii
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u 119.(THPT Chuyên Lê Thánh Tông 2019) Tìm s phc
z
tha mãn
(2 ) 3 5z i z i
.
A.
23zi
. B.
23zi
. C.
23zi
. D.
23zi
.
Li gii
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u 120.(S GD và ĐT Ninh Bình 2019) Cho s phc
z
tha mãn
1 9 2z i z i
. Tìm đun
ca
z
.
A.
21z
. B.
7z
. C.
7z
. D.
29z
.
Li gii
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Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
u 121.(THPT S 1 Tư Nghĩa 2019) Cho số phức
z
thỏa mãn
2 4 4iz i z i
.
Tính mô đun cua số phức
z
.
A.
5z
. B.
5z
. C.
25z
. D.
2 13z
.
Li gii
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u 122.(THPT Phú Dc 2019) Trên tp s , tìm s thc
a
b
tha
2 1 2a b i i i
vi
i
là đơn vị o.
A.
0, 2ab
. B.
1
,1
2
ab
. C.
0, 1ab
. D.
1, 2ab
.
Li gii
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u 123.(S GD ĐT Quãng Bình 2019) Cho số phức
z
thỏa mãn
2 1 17z iz i
. Khi đó
z
bằng:
A.
6z
. B.
146z
. C.
10z
. D.
58z
.
Li gii
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u 124.(S GD và ĐT Quãng Nam 2019) Cho số phức
z
thỏa mãn
3 (1 ) 1 5z i z i
.
m mô đun của
z
.
A.
5z
. B.
5z
. C.
13z
. D.
10z
.
Li gii
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
u 125.(THPT Ngô Quyn 2019) Cho s phc
z
tha điu kin
2
1 2 4 20i z z i
. Tìm
z
.
A.
25z
. B.
7z
. C.
4z
. D.
5z
.
Li gii
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u 126.(THPT Đoàn Thượng 2019) Có bao nhiêu s phc
z
tha
1 2 13 2i z i z i
?
A. 4. B. 3. C. 2. D. 1.
Li gii
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u 127.(THPT Kim Liên 2017) Tìm nghiệm phức
z
của phương trình
2 3 1 10 .z z i
A.
12zi
. B.
12zi
. C.
12zi
. D.
12zi
.
Li gii
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u 128.(THPT Toàn Thắng 2019) Cho số phức
z
thỏa mãn:
1 2 . 15 z i z i i
.
Tìm môđun của số phức
z
?
A.
5z
. B.
4z
. C.
25z
. D.
23z
.
Li gii
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Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
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u 129.(THPT Chuyên KHTN 2019) Cho số phức
z
thỏa mãn
2 1 1z i z i
.
Môđun của số phức
z
bằng
A.
3
. B.
1
. C.
5
. D.
5
.
Li gii
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u 130.(THPT Chuyên Lý T Trng 2019)
Cho s phc
,z a bi a b
tha
2 3 2 16 3 .i z z i
Tính giá tr biu thc
3.P a b
A.
11P 
. B.
17P
. C.
1P 
. D.
1P
.
Li gii
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u 131.(THPT Đô Lương 2019) Cho s phc
z
tha mãn
3 . . 7 6i z i z i
.
Môđun của s phc
z
bng
A.
25
. B.
25
. C.
5
. D.
5
.
Li gii
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u 132.(THPT Chuyên Hà Tĩnh 2019) Cho s phc
z
tho mãn
1 2 2 3 4 12z i z i i
.
Tìm to độ đim
M
biu din s phc
z
.
A.
3;1M
. B.
3; 1M
. C.
1;3M
. D.
1;3M
.
Li gii
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 133.(THPT Chuyên Hà Tĩnh 2019) Cho s phc
z
tho mãn
2 3 1 2 8i z i z i
.
Khong cách t đim biu din cho s phc
z
trên mt phng to độ
Oxy
đến điểm
1;2M
bng
A.
1
. B.
2
. C.
3
. D.
4
.
Li gii
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Mức độ 3. Vận dụng
u 134.(THPT KonTum 2019) Cho hai s phc
34zi
2z m mi
m
tha mãn
z iz
. Tng tt c các giá tr ca
m
bng
A.
1
. B.
46
2
. C.
0
. D.
2
.
Li gii
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u 135.(THPT Kinh Môn Hải Dương 2019) S phc
z
thỏa mãn phương trình
2
z
z
z

A.
1 i
. B.
i
. C.
1
. D.
1 i
.
Li gii
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Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
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u 136.(THPT ơng Thế Vinh 2019) Có bao nhiêu số phức
z
thỏa mãn
2
2
2018 2019z z z
?
A. Vô số. B.
2
. C.
1
. D.
0
.
Li gii
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u 137.(THPT Kim Liên 2018) Cho
2
2
1.
zz
w
zz
vi
z
s phức tùy ý cho trước vi phn thc
và phn o khác 0. Mệnh đề nào dưới đây đúng ?
A.
w
là s o. B.
1w 
. C.
1w
. D.
w
là s thc.
Li gii
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u 138.(THPT Hàm Rồng 2019) Cho số phức
( , )z a bi a b R
thỏa mãn
2 1 0z i z i
1z
. Tính
P a b
.
A.
3P
. B.
1P 
. C.
5P 
. D.
7P
.
Li gii
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u 139.(THPT Ngô Sỹ Liên 2019) Tập hợp các nghiệm phức của phương trình
2
2
0zz
A. Tập hợp mọi số phức thuần ảo.B.
;0i
. C.
;0i
. D.
0
.
Li gii
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Câu 140.ng Thành Nam 2019) bao nhiêu s phc
z
thỏa mãn đồng thời các điều kin:
1z
2
4 2 3z 
.
A.
1
. B.
2
. C.
3
. D.
4
.
Li gii
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u 141.(THPT Chuyên Hùng Vương 2019)
Môđun của s phc
z
tha mãn
15z 
17 5 . 0z z z z
bng
A.
53
. B.
34
. C.
29
13
. D.
29
.
Li gii
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Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
u 142.(Chuyên Ngoi Ng Ni 2019) Có bao nhiêu s phc
z
tha mãn
12z i z i
1z
A. 0. B. 2. C. 1. D. 4.
Li gii
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u 143.(THPT Ngô Sỹ Liên 2019) Biết số phức
z
thỏa mãn.
1
1
3
1
z
zi
zi
zi
. Số phức
z
bằng:
A.
1zi
. B.
1zi
. C.
1zi
. D.
1zi
Li gii
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u 144.(THPT Yên Khánh Ninh 2019) Có bao nhiêu s phc
z
tha mãn
2
20zz
.
A.
1
. B.
4
. C.
2
. D.
3
.
Li gii
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
u 145.(THPT Kinh Môn 2019) Cho số phức
u
,
v
thỏa mãn:
10uv
3 4 2019uv
. Ta
43uv
A.
2890
. B.
2981
. C.
2891
. D.
2982
.
Li gii
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u 146.(THPT Đô Lương 2019)Có bao nhiêu s phc
z
tha mãn
6 8 2zi
. 64zz
.
A.
3
. B.
4
. C.
2
. D.
1
.
Li gii
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u 147.(S GD và ĐT Cn Thơ 2019)
Có bao nhiêu s phc
z
tha mãn
2 1 2z i z i
4 2 3 2zi
?
A.
3
. B.
1
. C.
0
. D.
2
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức và Các Phép Toán
49
Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
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u 148.ng Thành Nam) Có bao nhiêu s phc
z
thỏa mãn điều kin
.2z z z
2?z
A. 2. B. 3. C. 1. D. 4.
Li gii
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u 149.(S GD và ĐT Đin Biên 2019) Cho số phức
z
thoả mãn điều kiện
3 4 5zi
22
2 33z z i
. Môđun của số phức
2zi
bằng:
A.
5
B.
9
. C.
25
. D.
5
.
Li gii
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u 150.(THPT Nam Tiền Hải 2019) Cho s phc
z
tha mãn
2 7 3z z i z
. Tính
z
.
A.
5z
. B.
3z
. C.
13
4
z
. D.
25
4
z
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
50
Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 151.Tính mô đun của số phức
z
thỏa mãn
1 2 1 4 0z i z i i
với
i
là đơn vị ảo.
A.
6
. B.
5
. C.
2
. D.
3
.
Li gii
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u 152. Cho số phức
; z a bi a b
thỏa mãn điều kiện
2
2.4zz
Đặt
22
8 12.aPb
Mệnh đề nào dưới đây đúng?
A.
2
2Pz
. B.
2
2
4Pz
. C.
2
4Pz
. D.
2
2
2Pz
.
Li gii
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u 153.(THPT Nam Tiền Hải Thái Bình 2019)
Cho số phức
, z a bi a b
thỏa mãn
1 2 3 2 i z z i
. Tính
P a b
.
A.
1P
. B.
1
2
P
. C.
1
2
P
. D.
1P
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức và Các Phép Toán
51
Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
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u 154.(THPT Nguyn Tt Thành)Cho s phc
z a bi
, ab
tha mãn
1 3 0z i z i
.
Tính
23S a b
.
A.
6S 
. B.
6S
. C.
5S 
. D.
5S
.
Li gii
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u 155.(THPT NQuyền Hà Nội 2019) Cho số phức
z
thỏa mãn
1 2 3i z i z
.
Môđun của số phức
2
1
iz
w
i
là?
A.
122
5
. B.
3 10
2
. C.
45
4
. D.
122
2
.
Lời giải
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u 156.(Đặng Thành Nam)
Cho số phức
( , ; , 0)z a bi a b a b
thỏa mãn
5
4 2 2 .
3
z z i z



Tính
2
.
2
ab
S
ab
A.
2 2 3S
. B.
2 2 2S 
. C.
2 2 2S 
. D.
2 2 3S 
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
52
Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
u 157.(THPT Nguyễn Đức Cảnh) Cho số phức
z a bi
(với
,ab
là các số thực và
22
0ab
)
thỏa mãn điều kiện
2
(2 )z i z z
. Tính
22
2S a b ab
.
A.
3S
. B.
1S 
. C.
2S
. D.
1S
.
Li gii
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u 158.ng Thành Nam) Có bao nhiêu s phc
z
tha mãn
( 2 3 ) 4 (4 5 ) .z z i i i z
A. 1. B. 2. C. 4. D. 3.
Li gii
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u 159.(THPT Chuyên Bc Giang 2019)
Tìm mô đun của s phc s
z
biết
2 1 1 1 1 2 2z i z i i
.
A.
1
9
. B.
2
3
. C.
2
9
. D.
1
3
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức và Các Phép Toán
53
Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
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u 160.(THPT Chuyên Nguyn Du 2109) Phương trình
3
zz
có bao nhiêu s phc?
A.
3
. B.
5
. C.
2
. D.
4
.
Li gii
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u 161.(Sở GD và ĐT Quãng Bình 2019)
Có bao nhiêu số phức
z
thỏa mãn
3 2 12z z z z
2 3 4z i z i
?
A. 1. B. 4. C. 3. D. 2.
Li gii
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u 162.(Triu Thái Vĩnh Phúc 2019) Cho s phc
z
tha mãn
5z
3 3 10z z i
.
Tìm s phc
w 4 3zi
.
A.
w 3 8i
. B.
w 1 3i
. C.
w 1 7i
. D.
w 4 8i
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
54
Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 163.(Chuyên ĐH Vinh) Có bao nhiêu s phc tha mãn ?
A. 4. B. 2. C. 1. D.3.
Li gii
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Mức độ 4. Vận dụng cao
u 164.(THPT Ninh Bình 2019) Cho số phức
z
có phần thực là số nguyên và
z
thỏa mãn
2 7 3z z i z
. Tính mô-đun của số phức
2
1 zz
bằng
A.
37
. B.
457
. C.
425
. D.
445
.
Li gii
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z
2
2019
11z z z i z z i
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức và Các Phép Toán
55
Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
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u 165.(THPT Chuyên Trần Đại Nghĩa 2019)
Cho số phức
z a bi
, , 0a b a
thỏa
. 12 13 10z z z z z i
. Tính
S a b
.
A.
7S
. B.
17S
. C.
17S 
. D.
5S
.
Li gii
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u 166.(THPT Thch Thành 2019)
Có bao nhiêu s phc
z
tha mãn
2
24 z z z
1 3 3 z i z i
?
A.
4
. B.
3
. C.
1
. D.
2
.
Li gii
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u 167.(Cụm 8 trường Chuyên 2019) Cho số phức
z
thỏa mãn
2
3 1 2z z i
. Phần ảo của
z
A.
3
4
. B.
3
4
. C.
2
. D.
2
.
Li gii
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u 168.ng Thành Nam 2019) Cho hai s phc
z
w
khác
0
tho mãn
35z w w
2 2 2 .z wi z w wi
Phn thc ca s phc
z
w
bng
A. 1. B.
3
. C.
1
. D. 3.
Li gii
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
56
Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 169.(THPT Lê Qúy Đôn 2019) Cho s phc
z
tho mãn
22
21z z i
. Tính môđun của s
phc
2zi
.
A.
1
. B.
3
. C.
4
. D.
2
.
Li gii
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u 170.Cho số phức thỏa nãm . Điểm biểu diễn s phc có tọa độ
A. . B. . C. . D. .
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u 171.(Tp Chí Toán Hc 2019) Cho số phức
1z
thỏa mãn
3
1z
.
Tính
2018 2018
11z z z z
.
A.
1
. B.Đáp số khác. C.
4
. D.
2
.
Li gii
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z
2 11 8z z i
z
3; 4
3; 4
3;4
3;4
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Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
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u 172.(THPT Chuyên Bc Giang 2019)
Có bao nhiêu s phc
z
thỏa mãn điều kin
5 5 6z i z i
, biết
z
có môđun bằng
5
?
A.
3
. B.
4
. C.
2
. D.
0
.
Li gii
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u 173.(THPT KonTum 2019)
Có bao nhiêu s phc
z
tha mãn
2 3 1z i z i
2
25z z z
?
A.
1
. B.
0
. C.
2
. D.
4
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 174.(nh Truyền Hình VTV 7-2019) Cho số phức
1
,
1 2 1
m
zm
mi


.
Tìm các giá trị của
m
để
| | 1zi
.
A.
0
. B.
1
. C.
4
. D. vô s.
Li gii
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u 175.(THPT Chuyên Quý Đôn 2019) Tính tổng của tất cả các giá trị của tham số
m
để tồn
tại duy nhất số phức
z
thoả mãn đồng thời
zm
2
43z m mi m
.
A.
4
. B.
6
. C.
9
. D.
10
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
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u 176.(THPT Kim Liên 2019) Cho s phc
z
tha mãn
23z z i
. Giá tr ca biu thc
1
z
z
A.
31
22
i
. B.
11
22
i
. C.
31
22
i
. D.
11
22
i
.
Li gii
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u 177.(THPT Gia Lc 2019)
Cho số phức
z
thỏa mãn điều kiện
6
1
23
zi
iz
. Tìm khẳng định đúng.
A.
1
3
z
. B.
1z
. C.
1
.
3
z
. D.
1z
.
Li gii
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u 178.(THPT Chuyên Lý T Trng 2019) Cho s phc
z
tha mãn
12z 
và s phc
1 3 2w i z
. Tính giá tr ca biu thc
33A w i
A. 8. B. 12. C. 6. D. 4.
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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Nhómi toán 5. Các số phức
z
thỏa mãn biểu thức số phức là số thực, số thuần ảo
1. Phương pháp.
Áp dng tính cht số phức
z a bi
được gọi là:
Số phức
z
thuần ảo
phần thực
0a
Số phức
z
là số thực
phần ảo
0.b
2. Bài tập minh họa.
Bài tp 17. Có bao nhiêu số phức
z
thỏa mãn
2 2 2zi
2
( 1)z
là số thuần ảo ?
Li gii
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3. Câu hỏi trắc nghiệm.
Mức độ 3. Vận dụng
u 179.(THPT Chuyên Hà Tĩnh 2019) Cho s phc
z
tha mãn
15z 
,
1 1 5
17z
z

z
phn o âm. Tìm tng phn thc và phn o ca
z
.
A.
2
. B.
4
. C.
6
. D.
8
.
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
Li gii
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u 180.(THPT Chuyên Hà Tĩnh 2019) Cho s phc
z
tha mãn
25z 
,
1 1 10
41z
z

z
phn ảo dương. Tìm tổng phn thc và phn o ca
z
.
A.
2
. B.
1
. C.
9
. D.
8
.
Li gii
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u 181.(THPT Chuyên Hà Tĩnh 2019) Cho s phc
z
tha mãn
15z 
,
1 1 5
17z
z

z
phn ảo dương. Tìm tổng phn thc và phn o ca
z
.
A.
2
. B.
4
. C.
6
. D.
8
.
Li gii
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u 182.(THPT Tư Nghĩa 2019) bao nhiêu số phức
z
thỏa mãn
1 10zi
2
4
z
z
là số
thuần ảo.
A.
4.
B.
2.
C.
3.
D.
1.
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 183.(THPT Chuyên Nguyn Du 2019) Cho các s phc
z
thỏa mãn hai điều kin
2z
2
z
là s thun o. Tổng bình phương phần thc ca tt c các s phc
z
đó bằng
A.
5
. B.
4
. C.
2
. D.
3
.
Li gii
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u 184. Có bao nhiêu s phc
z
tha mãn
1z
1
1
z
z
là s thun o?
A. Vô s. B.
0
. C.
2
. D.
4
.
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
u 185.(THPT NewTơn 2018) Có bao nhiêu số phức
z
thoả mãn
35zi
4
z
z
là số
thuần ảo?
A.
0
. B. vô số. C.
1
. D.
2
.
Li gii
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u 186.(Đặng Thành Nam) Có bao nhiêu số phức
z
thỏa mãn
2
z z z z z
2
z
là số
thuần ảo.
A. 4. B. 2. C. 3. D. 5.
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u 187.(THPT Kim Liên 2017) Tìm tập hợp
T
gồm tất cả các số phức
z
thỏa mãn đồng thời hai
điều kiện
2z
2
z
là số thuần ảo.
A.
1 ;1 ; 1 ;1T i i i i
. B.
1 ;1T i i
.
C.
1Ti
. D.
1Ti
.
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 188.(THPT ISCHOOL Nha Trang 2019) Cho s phc
z
không phi là s thc và
2
2
24
24
zz
zz


là
s thc. Có bao nhiêu s phc
z
tha mãn
2
z z z z z
?
A.
0
. B.
2
. C.
4
. D.
8
.
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Nhómi toán 6. Nhóm bài toán lấy môđun hai vế của đẳng thức số phức
1. Phương pháp.
K thut lấy môđun hai vế đùng để tính
z
hoc
Pz
. Ta thường làm như sau:
Sử dụng phép kéo theo của hai số phức bằng nhau
1 2 1 2
.z z z z
Kỹ thuật này chỉ được thực hiện được khi biểu thức giả thiết của bài toán được đưa về các dạng
chuẩn sau:
Dạng 1 :
,a bi c di
với
, , , .a b c d
Dạng 2 :
()a bi z c di
hoặc
()a bi z c di
với
, , , .a b c d
Dạng 3 :
a bi
ci d
z

hoặc
a bi
ci d
z

với
, , , .a b c d
Ta thường sử dụng các tính chất
22
, .z z z z z z
1 2 1 2
. . .z z z z
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
2. Câu hỏi trắc nghiệm .
u 189.(Chuyên Đi Học Sư Phạm Hà Ni 2019)
Gi
S
là tp hp các s phc
z
thỏa mãn điều kin
4
zz
. S phn t ca
z
A.
7
. B.
6
. C.
5
. D.
4
.
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u 190.Cho s phc
w
tha mãn
2
1w i z
, biết
zm
. Tính
w
.
A.
wm
. B.
2wm
. C.
2wm
. D.
4wm
.
Li gii
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u 191.(Đặng Thành Nam 2019) Cho số phức
z a bi
,ab
thỏa mãn
2 3 4z iz z
.
Tính
S ab
.
A.
3
2
S
. B.
3
2
S 
. C.
3
4
S
. D.
3
4
S 
.
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u 192.Cho số phức
z
thỏa mãn
4 (1 ) (4 3 ) .z i z z i
Mệnh đề nào sau đây đúng ?
A.
0 1.z
B.
1 3.z
C.
3 10.z
D.
10 50.z
Li gii
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
66
Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 193.(THPT Chuyên Thái Bình 2019)
Số phức
z a bi
,
,ab
là nghiệm của phương trình
11
1
z iz
i
z
z

. Tổng
22
T a b
bằng
A.
4
. B.
4 2 3
. C.
3 2 2
. D.
3
.
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u 194.ng Thành Nam) Có bao nhiêu số phức
z
thỏa mãn
2
3
10
4
z z i i
?
A.
1
. B.
3
. C.
2
. D.
0
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức và Các Phép Toán
67
Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
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u 195.(Sở GD Và ĐT Lạng Sơn 2019) Giả sử
12
,zz
là hai nghiệm phức của phương trình
2 1 2 1 3i z z i z i
12
1zz
. Tính
12
23M z z
.
A.
19M
. B.
19M
. C.
25M
. D.
5M
.
Li gii
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u 196.(THPT Yên A 2019) Có bao nhiêu s phc
z
tha mãn
5 2 6z z i i i z
?
A.
1
. B.
3
. C.
4
. D.
2
.
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u197.(THPT Chuyên Quốc Học Huế 2018)
Tìm môđun của số phức
z
biết
4 1 i 4 3 iz z z
.
A.
1
2
z
. B.
2z
. C.
4z
. D.
1z
.
Li gii
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
68
Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u198. (THPT Ngc To 2018) Cho hai s phc
z
,
w
tha mãn
3z
1 1 1
z w z w

.
Khi đó
w
bng:
A.
3
.
B.
1
2
. C.
2
. D.
1
3
.
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u 199.(Đề Chính Thức 2018) Có bao nhiêu số phức
z
thỏa mãn
3 2 4z z i i i z
?
A.
1
. B.
3
. C.
2
. D.
4
.
Li gii
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u 200.(Đề Chính Thức 2018) Có bao nhiêu số phức thỏa mãn
6 2 7z z i i i z
?
A.
2
. B.
3
. C.
1
. D.
4
.
Li gii
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức và Các Phép Toán
69
Lớp Toán Thầy Diệp Tuân Tel: 0935.660.880
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u 201. (Đề Minh Họa 2017) Cho số phức
z
thỏa mãn
10
1 2 2i z i
z
. Mệnh đề nào dưới
đây đúng?
A.
3
2.
2
z
B.
2.z
C.
1
.
2
z
D.
13
.
22
z
Li gii
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u 202. Cho số phức
z
thỏa mãn
4
3 4 8iz
z
. Trên mặt phẳng tọa độ, gọi
d
là khoảng cách
từ gốc tọa độ đến điểm biểu diễn số phức
z
. Mệnh đề nào sau đây đúng?
A.
9
.
4
d
B.
15
.
44
d
C.
1
0.
4
d
D.
19
.
24
d
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IVBài 1. Số Phức và Các Phép Toán
70
Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 203. Tìm môđun của số phức
z
biết
4 1 4 3z i z z i
.
A.
1.z
B.
4.z
C.
2.z
D.
1
.
2
z
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u 204. Xét số phức
z
thỏa mãn
2
1 2 1z i z i
. Mệnh đề nào sau đây đúng?
A.
2.z
B.
4 2.z
C.
3 2 4 2.z
D.
2 3 2.z
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức Các Phép Toán
71
Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
Nhómi toán 7. Chuẩn hóa số phức.
1. Phương pháp.
K thut chuẩn hóa môđun thường dùng trong bài toán cho nhiu s phức như :
12
zz
hoc
1 2 3
z z z
hoc
12
...zz
Để giải bài toán này ta thường chọn
1
1z
rồi áp dụng các tính chất sau :
1 2 1 2
. . ,z z z z
22
, .z z z z z z
hoc công thc hình bình hành:
22
22
1 2 1 2 1 2
2 z z z z z z
Đặc biệt: Nếu
12
1zz
thì ta chn các s phc sau
1 3 2 2
1, , , .
2 2 2 2
z z i z i z i
2. Câu hỏi trắc nghiệm .
u 205.Cho các số phức
12
0, 0zz
thỏa mãn
1 2 1 2
.z z z z
Giá trị của biểu thức
44
12
21
zz
P
zz

A.
1
. B.
1
. C.
3
. D.
4
.
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u 206. Cho ba số phức
1 2 3
, , z z z
thỏa mãn
1 2 3 1 2 3 1 2 3
1z z z z z z z z z
. Tính giá trị của
biểu thức
2017 2017 2017
1 2 3
.P z z z
A.
2017.P
B.
6051.P
C.
0.P
D.
1.P
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u 207.(Tp chí THTT 2018) Cho hai s phc
1
z
,
2
z
tha mãn
1
1z
,
2
2z
12
3zz
.
Giá tr ca
12
zz
A.
0
. B.
1
. C.
2
. D. mt giá tr khác.
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức và Các Phép Toán
72
Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 208.(Sở GD và ĐT Hải Dương) Cho các số phức
1
z
,
2
z
thoả mãn
12
3zz
,
12
1zz
.
Tính
1 2 1 2
z z z z
.
A.
1 2 1 2
0z z z z
. B.
1 2 1 2
2z z z z
. C.
1 2 1 2
1z z z z
. D.
1 2 1 2
1z z z z
.
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u 209. Cho hai số phức
12
,zz
thỏa mãn
1 2 1 2
1.z z z z
Tính
12
.zz
A.
3.
B.
2 3.
C.
3.
D.
3
.
2
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u 210. Cho
1
z
,
2
z
là hai số phức thỏa mãn
22z i iz
, biết
12
1zz
.
Tính giá trị của biểu thức
12
P z z
.
A.
3
.
2
P
B.
2.P
C.
2
.
2
P
D.
3.P
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức Các Phép Toán
73
Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 211. Cho
1
z
,
2
z
là hai số phức thỏa mãn
12
6, 8zz
12
2 13.zz
Tính giá trị của biểu thức
12
23P z z
.
A.
1008.P
B.
12 7.P
C.
36.P
D.
5 13.P
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u 212. Cho số phức
z
thỏa mãn
1
1zz
z
. Tính môđun số phức
1wz
.
A.
5.w
B.
5.w
C.
1.w
D.
3.w
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u 213. Cho hai số phức
12
, zz
thỏa mãn
12
1zz
12
3 4 1zz
. Tính môđun của số phức
12
3 4 .z z z
A.
5 2.z
B.
7.z
C.
4 3.z
D.
2 3.z
Li gii
Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức và Các Phép Toán
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 214.(THPT Chuyên KHTN)
Vi
1
z
,
2
z
là hai s phc bt k, giá tr ca biu thc
22
12
22
1 2 1 2
zz
a
z z z z
bng.
A.
1
2
a
. B.
1a
. C.
3
2
a
. D.
2a
.
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u 215.(Chuyên ĐH Vinh) Cho hai số phức
12
,zz
thỏa mãn
1 2 1 2
1z z z z
. Tính
12
zz
.
A.
1
. B.
23
. C.
3
2
. D.
3
.
Li gii
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u 216.(THPT Nguyễn Huệ 2019) Xét các số phức
12
, zz
thỏa
12
12
13
52
zz
zz


. Hãy tính
12
zz
.
A.
3
. B.
2
. C.
2
. D.
3
.
Li gii
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Trung Tâm Luyện Thi Đại Học Amsterdam Chương IV–Bài 1. Số Phức Các Phép Toán
75
Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 217.(THPT chuyên KHTN) Cho
1 2 3
,,z z z
là các s phc thõa mãn
1 2 3
1z z z
.
Khẳng định nào sau đây đúng?
A.
1 2 3 1 2 2 3 3 1
z z z z z z z z z
.
B.
1 2 3 1 2 2 3 3 1
z z z z z z z z z
.
C.
1 2 3 1 2 2 3 3 1
z z z z z z z z z
. D.
1 2 3 1 2 2 3 3 1
z z z z z z z z z
.
Li gii
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u 218.Cho hai số phức
1
z
2
z
thỏa mãn
1
3z
,
2
4z
,
12
37zz
.
Xét số phức
1
2
z
z a bi
z
. Tìm
b
.
A.
33
8
b
. B.
39
8
b
. C.
3
8
b
. D.
3
8
b
.
Li gii
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
u 219.(THPT Hoàng Hoa Thám 2019) Cho số phức
z
mođun bằng
2017
w
số phức
thỏa biểu thức
1 1 1
z w z w

. Mođun của số phức
w
là:
A.
2016
. B.
2017
. C.
1
. D.
2
.
Li gii
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u 220.(THPT Chuyên Thái Nguyên) Cho s phc
z a bi
,ab
tha mãn phương trình
11
1
z iz
i
z
z

. Tính
22
ab
.
A.
3 2 2
. B.
4
. C.
3 2 2
. D.
2 2 2
.
Li gii
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u 221. Cho hai s phc
12
, zz
tha n
1
3z
,
2
2z
được biu din trong mt phng phc ln
lượt các điểm
, MN
. Biết góc tạo bi giữa hai vectơ
OM
ON
bằng
0
30
. Tính g tr ca biu
thc
12
12
.
zz
A
zz
A.
1.A
B.
13.A
C.
73
.
2
A
D.
1
.
13
A
Li gii
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 222. Cho hai số phức
12
, zz
thỏa mãn
12
1zz
12
10zz
. Tìm phần ảo
a
của số phức
12
12
1
zz
w
zz
.
A.
0.a
B.
1.a
C.
1.a 
D.
2.a
Li gii
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u 223. Cho hai số phức
12
, zz
thỏa mãn
12
2, 1zz
12
2 3 4zz
. Tính giá trị của biểu
thức
12
2.M z z
A.
4.M
B.
2.M
C.
11.M
D.
5.M
Li gii
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u 224. Cho số phức
, zw
khác
0
2.z w z w
Tìm phần thực
a
của số phức
.
z
u
w
A.
1
.
8
a 
B.
1
.
4
a
C.
1.a
D.
1
.
8
a
Li gii
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 225. Cho hai số phức
12
, zz
thỏa
1 2 1 2
0, 0, 0z z z z
1 2 1 2
1 1 2
.
z z z z

Tính giá trị biểu
thức
1
2
.
z
P
z
A.
2 3.P
B.
2
.
3
P
C.
3
.
2
P
D.
2
.
2
P
Li gii
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u 226. Cho hai số phức
12
, zz
thỏa mãn điều kiện
1 2 1 2
1.z z z z
Tính giá trị của biểu thức
22
12
21
.
zz
P
zz

A.
1.Pi
B.
1.Pi
C.
1.Pi
D.
1.P 
Li gii
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 227. Cho số phức
0z
sao cho
z
không phải là số thực và
2
1
z
w
z
là số thực.
Tính giá trị của biểu thức
2
.
1
z
P
z
A.
1
.
5
P
B.
1
.
2
P
C.
2.P
D.
1
.
3
P
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u 228. Cho các số phức
1 2 3
,,z z z
thỏa mãn
1 2 3
1z z z
1 2 3
z z z a
. Tính giá trị biểu
thức
1 2 2 3 3 1
P z z z z z z
theo
a
.
A.
2
3Pa
. B.
3Pa
. C.
Pa
. D.
2
Pa
.
Li gii
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Lớp Toán Thầy–Diệp Tuân Tel: 0935.660.880
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u 229. Cho ba số phức
23
, , z z z
thỏa mãn điều kiện
1 2 3
1z z z
1 2 3
0z z z
.
Tính giá trị biểu thức
222
1 2 3
A z z z
.
A.
1A
. B.
0A
. C.
1A 
. D.
2A
.
Li gii
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