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: 17

Answer

1. $\lambda_1=1+ 3i $ and $\lambda_2=1- 3i$ 2. $\vec{V}=(-(1-i),1)r$ $\vec{V}=(-(1+i),1)r$

Work Step by Step

1. Find eigenvalues: (A-$\lambda$I)$\vec{V}$=$\vec{0}$ $\begin{bmatrix} -2-\lambda &-6 \\ 3 & 4-\lambda \end{bmatrix}\begin{bmatrix} v_1\\ v_2 \end{bmatrix}=\begin{bmatrix} 0\\ 0 \end{bmatrix}$ $\begin{vmatrix} -2-\lambda &-6 \\ 3 & 4-\lambda \end{vmatrix}=0$ $\lambda_1=1+ 3i $ and $\lambda_2=1- 3i$ 2. $\lambda_1=1+ 3i$ let $B=A-\lambda_1I$ $B= \begin{bmatrix} -2-\lambda_1 &-6 \\ 3 & 4-\lambda_1 \end{bmatrix}$ = $\begin{bmatrix} -3 - 3i& -6\\ 3& 3 + 3i \end{bmatrix}$ Then, $B\vec{V}$=$\vec{0}$ Use reduced row echelon form $[B|\vec{0}]$= \[ \left(\begin{array}{@{}cc|c@{}} 1 & 1-i & 0 \\ 0 & 0 & 0 \\ \end{array}\right) \] let $r$ is a free variable. Then $x_1=-(1-i)x_2 = -(1-i) r$ $\vec{V}=(-(1-i),1)r$ ============================= $\lambda_2=1- 3i$ let $B=A-\lambda_1I$ $B= \begin{bmatrix} -2-\lambda_2 &-6 \\ 3 & 4-\lambda_2 \end{bmatrix}$ = $\begin{bmatrix} -3 + 3i& -6\\ 3& 3 + 3i \end{bmatrix}$ Then, $B\vec{V}$=$\vec{0}$ Use reduced row echelon form $[B|\vec{0}]$= \[ \left(\begin{array}{@{}cc|c@{}} 1 & 1+i & 0 \\ 0 & 0 & 0 \\ \end{array}\right) \] let $r$ be a free variable. Then $x_1=-(1+i)x_2 = -(1+i) r$ $\vec{V}=(-(1+i),1)r$
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