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Linear Algebra Exercises and Problems
1. Determine a basis of Im(f ) and of Ker(f ) in each of the following cases.
(a) f : R2 → R2, (x1, x2) 7→ (x1 + x2, x1 − 2x2)
(b) f : R3 → R2, (x1, x2, x3) 7→ (x1 − x2 − x3, 0)
(c) f : R2 → R3, (x1, x2) 7→ (x1 + x2, 0, x1 − x2)
(d) f : R3 → R2, (x1, x2, x3) 7→ (x1 + 2x2 + 3x3, x1 − x2 − x3)
(e) f : R4 → R4, (x1, x2, x3, x4) 7→ (x4, x3, x2, x1)
2. In Exercise 1, which linear mapping is injective, surjective, bijective?
3. Let f : V → W be a linear mapping and W 0 a subspace of W . Show that f −1(W 0) is a subspace of V .
4. Solve the following systems of simultaneous linear equations. −2x + 3y + 3z = −9 (a) 3x − 4y + z = 5 x + 2y − z = 2 (b) x + 4y − 3z = 3 x1 − x2 + x3 − x4 = 1 (c) −x1 + x2 + x3 + x4 = 2 x1 + x2 − x3 + x4 = 3 x1 + x2 + 2x3 − x4 = 4 (d) 3x2 − x3 + 4x4 = 2 x1 + 2x2 − 3x3 + 5x4 = 0
5. Let there be given a linear mapping f : V → W . Show that if dim V > dim W then f is not injective.
6. Let f : V → W be an injective linear mapping. Suppose that {~x1, . . . , ~xk} are linearly
independent vectors in V . Show that {f ( ~x1), . . . , f(~xk)} are linearly independent vectors in W .
7. Show that if f : R4 → R2 is a linear mapping so that
Ker(f ) = {(x1, x2, x3, x4) ∈ R4 : x1 = 5x2, x3 = 7x4}, then f is surjective.
8. Let f : P1 → R be a linear map given by f(P ) = P (1). Find the image and kernel of
f . Show a basis for each of them. 1