Differential Equations and Linear Algebra (4th Edition)

Published by Pearson
ISBN 10: 0-32196-467-5
ISBN 13: 978-0-32196-467-0

Chapter 7 - Eigenvalues and Eigenvectors - 7.1 The Eigenvalue/Eigenvector Problem - Problems - Page 444: 13

Answer

See below

Work Step by Step

1. Find eigenvalues: (A-$\lambda$I)$\vec{V}$=$\vec{0}$ $\begin{bmatrix} 1-\lambda & 6 \\ 2 & -3-\lambda \end{bmatrix}\begin{bmatrix} v_1\\ v_2 \end{bmatrix}=\begin{bmatrix} 0\\ 0 \end{bmatrix}$ $\begin{bmatrix} 1-\lambda & 6 \\ 2 & -3-\lambda \end{bmatrix}=0$ $\left (1- \lambda \right )\left (- \lambda -3 \right )+12=0$ $\lambda^2+2\lambda -15=0$ $\lambda_1=3$ and $\lambda_2=-5$ 2. Find eigenvectors: For $\lambda_1=3$ let $B=A-\lambda_1I$ $B= \begin{bmatrix} 1-\lambda_1 & 6 \\ 2 & -3-\lambda_1 \end{bmatrix}= \begin{bmatrix} -2 & 6 \\ 2 &-6 \end{bmatrix}$ Then, $B\vec{V}$=$\vec{0}$ Use reduced row echelon form $[B|\vec{0}]$= \[ \left(\begin{array}{@{}cc|c@{}} 1 & -3 & 0 \\ 0 & 0& 0 \\ \end{array}\right) \] let $r$ is a free variable. Then $x_1=3x_2 = 3r$ $\vec{V}=(3,1)r$ For $\lambda_1=-5$ let $B=A-\lambda_1I$ $B= \begin{bmatrix} 1-\lambda_1 & 6 \\ 2 & -3-\lambda_1 \end{bmatrix}= \begin{bmatrix} 6 & 6 \\ 2 &2 \end{bmatrix}$ Then, $B\vec{V}$=$\vec{0}$ Use reduced row echelon form $[B|\vec{0}]$= \[ \left(\begin{array}{@{}cc|c@{}} 1 & 1 & 0 \\ 0 & 0& 0 \\ \end{array}\right) \] let $r$ is a free variable. Then $x_1=-x_2 = -r$ $\vec{V}=(-1,1)r$
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