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: 28

Answer

$\lambda_1=0$ $\vec{V}=(-0.6,1.8,1)r$ $\lambda_2=4$ $\vec{V}=(1,1,1)t$ $\lambda_3=2$ $\vec{V}=(1,3,1)s$

Work Step by Step

1. eigenvalues: (A-$\lambda$I)$\vec{V}$=$\vec{0}$ $\begin{bmatrix} 2-\lambda &-1 &3 \\ 3& 1-\lambda&0\\ 2&-1 &3-\lambda \end{bmatrix}\begin{bmatrix} v_1\\ v_2\\ v_3 \end{bmatrix}=\begin{bmatrix} 0\\ 0\\ 0 \end{bmatrix}$ $\begin{vmatrix} 2-\lambda &-1 &3 \\ 3& 1-\lambda&0\\ 2&-1 &3-\lambda \end{vmatrix}=0$ $\lambda_1=0$ $\lambda_2=4$ $\lambda_3=2$ =============================== 2. eigenvectors $\lambda_1=0$ let $B=A-\lambda_1I$ $B= \begin{bmatrix} 2-\lambda_1 &-1 &3 \\ 3& 1-\lambda_1&0\\ 2&-1 &3-\lambda_1 \end{bmatrix}$ = $\begin{bmatrix} 2&-1 &3 \\ 3& 1&0\\ 2&-1 &3 \end{bmatrix}$ Then, $B\vec{V}$=$\vec{0}$ Use reduced row echelon form $[B|\vec{0}]$= \[ \left(\begin{array}{@{}ccc|c@{}} 1 & 0 & 0 .6& 0 \\ 0 & 1 & -1.8 & 0 \\ 0 & 0 & 0 & 0 \end{array}\right) \] let $r$ is a free variable. $\vec{V}=(-0.6,1.8,1)r$ ============================= $\lambda_2=4$ let $B=A-\lambda_2I$ $B= \begin{bmatrix} 2-\lambda_2 &-1 &3 \\ 3& 1-\lambda_2&0\\ 2&-1 &3-\lambda_2 \end{bmatrix}$ = $\begin{bmatrix} -2&-1 &3 \\ 3& -3&0\\ 2&-1 &-1 \end{bmatrix}$ Then, $B\vec{V}$=$\vec{0}$ Use reduced row echelon form $[B|\vec{0}]$= \[ \left(\begin{array}{@{}ccc|c@{}} 1 & 0 & -1 & 0 \\ 0 & 1 & -1& 0 \\ 0 & 0 & 0 & 0 \end{array}\right) \] let $t$ is a free variable. $\vec{V}=(1,1,1)t$ ============================= $\lambda_3=2$ let $B=A-\lambda_3I$ $B= \begin{bmatrix} 2-\lambda_3 &-1 &3 \\ 3& 1-\lambda_3&0\\ 2&-1 &3-\lambda_3 \end{bmatrix}$ = $\begin{bmatrix} 0&-1 &3 \\ 3& -1&0\\ 2&-1 &1 \end{bmatrix}$ Then, $B\vec{V}$=$\vec{0}$ Use reduced row echelon form $[B|\vec{0}]$= \[ \left(\begin{array}{@{}ccc|c@{}} 1 & 0 & -1 & 0 \\ 0 & 1 & -3& 0 \\ 0 & 0 & 0 & 0 \end{array}\right) \] let $s$ is a free variable. $\vec{V}=(1,3,1)s$
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