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: 20

Answer

$\lambda=2$ $\vec{V}=(1.5,1,0)r-(-1,0,1)s$

Work Step by Step

1. eigenvalues: (A-$\lambda$I)$\vec{V}$=$\vec{0}$ $\begin{bmatrix} 10-\lambda &-12 &8 \\ 0& 2-\lambda&0\\ -8&12 &-6-\lambda \end{bmatrix}\begin{bmatrix} v_1\\ v_2\\ \end{bmatrix}=\begin{bmatrix} 0\\ 0 \end{bmatrix}$ $\begin{vmatrix} 10-\lambda &-12 &8 \\ 0& 2-\lambda&0\\ -8&12 &-6-\lambda \end{vmatrix}=0$ $\lambda=2$ =============================== 2. eigenvectors $\lambda_1=2$ let $B=A-\lambda_1I$ $B= \begin{bmatrix} 10-\lambda &-12 &8 \\ 0& 2-\lambda&0\\ -8&12 &-6-\lambda \end{bmatrix}$ = $\begin{bmatrix} 8&-12&8 \\ 0 &0 &0\\ -8&12 &-8 \end{bmatrix}$ Then, $B\vec{V}$=$\vec{0}$ Use reduced row echelon form $[B|\vec{0}]$= \[ \left(\begin{array}{@{}ccc|c@{}} 1 & -1.5 & 1 & 0 \\ 0 & 0 & 0 & 0 \\ 0 & 0 & 0 & 0 \end{array}\right) \] let $r$ and $s$ is a free variable. Then $x_1=1.5x_2-1x_3 = 1.5r-1s$ $\vec{V}=(1.5,1,0)r-(-1,0,1)s$
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