1.6.4 Let A and P be n xn matrices with P invertible. It was shown in class that A and P-AP have the same eigenvalues. Use this fact to prove that if A and B are both invertible nx n matrices, then AB and BA have the same eigenvalues.

Linear Algebra: A Modern Introduction
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Chapter4: Eigenvalues And Eigenvectors
Section4.5: Iterative Methods For Computing Eigenvalues
Problem 4EQ
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1.5.1(f) Is the matrix
1 -1 0
-1 2 -1
I- 0
diagonalizable? If so, what are the corresponding diagonal matrix D and orthogonal matrix P?
In this case, show that P is indeed orthogonal.
1.6.4 Let A and P be n x n matrices with P invertible. It was shown in class that A and
P-AP have the same eigenvalues. Use this fact to prove that if A and B are both invertible
nx n matrices, then AB and BA have the same eigenvalues.
1.7.5 Use Theorem 1.7.1 or Theorem 1.7.2 (you can find them in the lecture notes) to determine
the definiteness of the following quadratic forms:
(a) Q= x}+8a,"
(b) Q= 5x² + 2x1x3 + 2x3 + 2x2X3 + 4x3,
(d) Q= -3x² + 2x1x2 – x² + 4x2X3 – 8x3.
1.7.6 Let A be an n x n symmetric positive semidefinite matrix. Prove that A is positive
definite if and only if det A # 0.
1.7.7(a) For what values of parameter c, is the quadratic form
Q(x, y) = 3x² – (5+ c)xy + 2cy²
(i) positive definite, (ii) positive semidefinite, and (iii) indefinite?
3:16 PM
2/22/2021
Transcribed Image Text:1/ 1 91% 1.5.1(f) Is the matrix 1 -1 0 -1 2 -1 I- 0 diagonalizable? If so, what are the corresponding diagonal matrix D and orthogonal matrix P? In this case, show that P is indeed orthogonal. 1.6.4 Let A and P be n x n matrices with P invertible. It was shown in class that A and P-AP have the same eigenvalues. Use this fact to prove that if A and B are both invertible nx n matrices, then AB and BA have the same eigenvalues. 1.7.5 Use Theorem 1.7.1 or Theorem 1.7.2 (you can find them in the lecture notes) to determine the definiteness of the following quadratic forms: (a) Q= x}+8a," (b) Q= 5x² + 2x1x3 + 2x3 + 2x2X3 + 4x3, (d) Q= -3x² + 2x1x2 – x² + 4x2X3 – 8x3. 1.7.6 Let A be an n x n symmetric positive semidefinite matrix. Prove that A is positive definite if and only if det A # 0. 1.7.7(a) For what values of parameter c, is the quadratic form Q(x, y) = 3x² – (5+ c)xy + 2cy² (i) positive definite, (ii) positive semidefinite, and (iii) indefinite? 3:16 PM 2/22/2021
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