Exercise 7.5.13 Specify whether each statement is true or false. If true, provide a proof. If false, provide a counterexample. (a) If A is a 3 x 3-matrix with determinant zero, then one column must be a multiple of some other column. (b) If any two columns of a square matrix are equal, then the determinant of the matrix equals zero. (c) For two nxn-matrices A and B, det(A + B) = det(A)+det(B).

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Can you please solve a, b & c ?

**Exercise 7.5.13** 

Specify whether each statement is true or false. If true, provide a proof. If false, provide a counterexample.

(a) If \( A \) is a \( 3 \times 3 \)-matrix with determinant zero, then one column must be a multiple of some other column.

(b) If any two columns of a square matrix are equal, then the determinant of the matrix equals zero.

(c) For two \( n \times n \)-matrices \( A \) and \( B \), \( \text{det}(A + B) = \text{det}(A) + \text{det}(B) \).

(d) For an \( n \times n \)-matrix \( A \), \( \text{det}(3A) = 3 \text{det}(A) \).

(e) If \( A^{-1} \) exists, then \( \text{det}(A^{-1}) = \text{det}(A)^{-1} \).

(f) If \( B \) is obtained by multiplying a single row of \( A \) by 4, then \( \text{det}(B) = 4 \text{det}(A) \).

(g) For an \( n \times n \)-matrix \( A \), we have \( \text{det}(-A) = (-1)^n \text{det}(A) \).

(h) If \( A \) is a real \( n \times n \)-matrix, then \( \text{det}(A^T A) \geq 0 \).

(i) If \( A^k = 0 \) for some positive integer \( k \), then \( \text{det}(A) = 0 \).

(j) If \( Ax = 0 \) for some \( x \neq 0 \), then \( \text{det}(A) = 0 \).
Transcribed Image Text:**Exercise 7.5.13** Specify whether each statement is true or false. If true, provide a proof. If false, provide a counterexample. (a) If \( A \) is a \( 3 \times 3 \)-matrix with determinant zero, then one column must be a multiple of some other column. (b) If any two columns of a square matrix are equal, then the determinant of the matrix equals zero. (c) For two \( n \times n \)-matrices \( A \) and \( B \), \( \text{det}(A + B) = \text{det}(A) + \text{det}(B) \). (d) For an \( n \times n \)-matrix \( A \), \( \text{det}(3A) = 3 \text{det}(A) \). (e) If \( A^{-1} \) exists, then \( \text{det}(A^{-1}) = \text{det}(A)^{-1} \). (f) If \( B \) is obtained by multiplying a single row of \( A \) by 4, then \( \text{det}(B) = 4 \text{det}(A) \). (g) For an \( n \times n \)-matrix \( A \), we have \( \text{det}(-A) = (-1)^n \text{det}(A) \). (h) If \( A \) is a real \( n \times n \)-matrix, then \( \text{det}(A^T A) \geq 0 \). (i) If \( A^k = 0 \) for some positive integer \( k \), then \( \text{det}(A) = 0 \). (j) If \( Ax = 0 \) for some \( x \neq 0 \), then \( \text{det}(A) = 0 \).
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