Elementary Linear Algebra 7th Edition

Published by Cengage Learning
ISBN 10: 1-13311-087-8
ISBN 13: 978-1-13311-087-3

Chapter 6 - Linear Transformations - 6.3 Matrices for Linear Transformations - 6.3 Exercises - Page 322: 9

Answer

$ \left[ {\begin{array}{*{20}{c}} 4\\ { - 2}\\ { - 2} \end{array}} \right]$

Work Step by Step

Take the standard basis for $R^2$, which is $(1,0),(0,1)=\{e_1,e_2\}$. Then, $T(1,0)=(1-0,1+2(0),0)=(1,1,0)\\ T(0,1)=(0-1,0+2(1),1)=(-1,2,1)$ Therefore, the matrix corresponding to linear the transformation $T$ is given by: $A=[T(e_1)$ $T(e_2)]$ $=\left[ {\begin{array}{*{20}{c}} 1&{ - 1}\\ 1&2\\ 0&1 \end{array}} \right]$ Hence, the image of $v=\left[ {\begin{array}{*{20}{c}} 2\\ { - 2} \end{array}} \right]$ is $\begin{array}{l} T(v) = Av\\ \Rightarrow T\left[ {\begin{array}{*{20}{c}} 2\\ { - 2} \end{array}} \right] = \left[ {\begin{array}{*{20}{c}} 1&{ - 1}\\ 1&2\\ 0&1 \end{array}} \right]\left[ {\begin{array}{*{20}{c}} 2\\ { - 2} \end{array}} \right] = \left[ {\begin{array}{*{20}{c}} 4\\ { - 2}\\ { - 2} \end{array}} \right] \end{array}$
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