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: 18

Answer

See below

Work Step by Step

1. Find eigenvalues: (A-$\lambda$I)$\vec{V}$=$\vec{0}$ $\begin{bmatrix} 3-\lambda & -2 \\ 4 & -1-\lambda \end{bmatrix}\begin{bmatrix} v_1\\ v_2 \end{bmatrix}=\begin{bmatrix} 0\\ 0 \end{bmatrix}$ $\begin{bmatrix} 3-\lambda & -2 \\ 4 & -1-\lambda \end{bmatrix}=0$ $\left (3- \lambda \right )\left (- \lambda -1 \right )+8=0$ $\lambda^2-2\lambda +5=0$ $\lambda_1=1+2i$ and $\lambda_2=1-2i$ 2. Find eigenvectors: For $\lambda_1=1+2i$ let $B=A-\lambda_1I$ $B=\begin{bmatrix} 3-\lambda & -2 \\ 4 & -1-\lambda \end{bmatrix}= \begin{bmatrix} 2-2i & -2 \\ 4 & -2-2i \end{bmatrix}$ Then, $B\vec{V}$=$\vec{0}$ Use reduced row echelon form $[B|\vec{0}]$= \[ \left(\begin{array}{@{}cc|c@{}} 1-i & 1 & 0 \\ 0 & 0& 0 \\ \end{array}\right) \] let $r$ is a free variable. Then $(1-i)x_1=x_2 = r$ $\vec{V}=(1,1-i)r$ For $\lambda_1=1-2i$ let $B=A-\lambda_1I$ $B=\begin{bmatrix} 3-\lambda & -2 \\ 4 & -1-\lambda \end{bmatrix}= \begin{bmatrix} 2+2i & -2 \\ 4 & -2+2i \end{bmatrix}$ Then, $B\vec{V}$=$\vec{0}$ Use reduced row echelon form $[B|\vec{0}]$= \[ \left(\begin{array}{@{}cc|c@{}} 1+i & 1 & 0 \\ 0 & 0& 0 \\ \end{array}\right) \] let $r$ is a free variable. Then $(1+i)x_1=x_2 = r$ $\vec{V}=(1,1+i)r$
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