Differential Equations and Linear Algebra (4th Edition)

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

Chapter 6 - Linear Transformations - 6.5 The Matrix of a Linear Transformation - Problems - Page 427: 12

Answer

See below

Work Step by Step

From Theorem 6.4.5: $$[T(A)]_C=[T]^C_B[A)]_B$$ a) Computing $[T]^C_B$ $T(E_{11})=\begin{bmatrix} 2.1-0+0 & -1+3.0\\ 0 & -1-0+3.0 \end{bmatrix}=\begin{bmatrix} 2 & -1 \\0 & -1 \end{bmatrix} \\ T(E_{12})=\begin{bmatrix} 2.0-1+0 & -0+3.0\\ 0 & -1-0+3.0 \end{bmatrix}=\begin{bmatrix} -1 & 0\\0 & -1 \end{bmatrix}\\ T(E_{21})=\begin{bmatrix} 2.0-0+0 & -0+3.0\\ 0 & -0-0+3.1 \end{bmatrix}=\begin{bmatrix} 0 & 0 \\0 & 3 \end{bmatrix}\\ T(E_{22})=\begin{bmatrix} 2.0-0+1 & 0+3.1\\ 0 & -0-0+3.0 \end{bmatrix}=\begin{bmatrix} 1 & 3 \\0 & 0 \end{bmatrix}$ then we have $T(E_{11})=\begin{bmatrix} 2 & -1 \\0 & -1 \end{bmatrix}=2.E_{11}-1.E_{12}+0.E_{21}-1.E_{22}\\ T(E_{12})=\begin{bmatrix} -1 & 0 \\0 & -1 \end{bmatrix}=-1.E_{11}+0.E_{12}+0.E_{21}-1.E_{22}\\ T(E_{21})=\begin{bmatrix} 0 & 0 \\0 & 3 \end{bmatrix}=0.E_{11}+0.E_{12}+0.E_{21}+3.E_{22}\\ T(E_{22})=\begin{bmatrix} 1 & 3\\0 & 0 \end{bmatrix}=1.E_{11}+3.E_{12}+0.E_{21}+0.E_{22}$ Therefore, $[T(E_{11})]_C=\begin{bmatrix} 2 \\ -1 \\ 0 \\ -1 \end{bmatrix}\\ [T(E_{12})]_C=\begin{bmatrix}-1 \\ 0 \\ 0 \\ -1 \end{bmatrix}\\ [T(E_{21})]_C=\begin{bmatrix} 0 \\ 0 \\ 0 \\ 3 \end{bmatrix}\\ [T(E_{22})]_C=\begin{bmatrix} 1 \\ 3 \\ 0 \\ 0 \end{bmatrix}$ Hence, $[T]_B^C=\begin{bmatrix} 2 & -1 & 0 & 1 \\ -1 & 0 & 0 & 3\\ 0 & 0 & 0 & 0 \\ -1 & -1 & 3 & 0 \end{bmatrix}$ We can notice that $[A]_B=\begin{bmatrix} -7 \\ 2 \\ 1 \\ 3 \end{bmatrix}$ Consequently, $[T(v)]_C=[T]^C_B[p(x)]_B=\begin{bmatrix} 2 & -1 & 0 & 1 \\ -1 & 0 & 0 & 3\\ 0 & 0 & 0 & 0 \\ -1 & -1 & 3 & 0 \end{bmatrix}\begin{bmatrix} -7 \\ 2 \\ 1 \\ 3 \end{bmatrix}=\begin{bmatrix} -19 \\ -2 \\ 0 \\ 8 \end{bmatrix}\\ \rightarrow T(A)=\begin{bmatrix} -19 & -2 \\ 0 & 8\end{bmatrix}$ b) From part (a), we obtain: $T(p(x))=T(\begin{bmatrix} -7 & 2 \\ 1 & -3\end{bmatrix})=\begin{bmatrix} 2.(-7)-2+(-3) & 7+3.(-3) \\ 0 & 7-2+3.1\end{bmatrix}=\begin{bmatrix} -19 & -2 \\ 0 & 8\end{bmatrix}$
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