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: 13

Answer

a) The matrix corresponding to linear transformation $T$ is given by: $=\left[ {\begin{array}{*{20}{c}} { -1}&{0}\\ 0&{ 1} \end{array}} \right]$ b) Hence, the image of $v=\left[ {\begin{array}{*{20}{c}} 2\\ {-3} \end{array}} \right]$ is $\left[ {\begin{array}{*{20}{c}} { -2}\\ { -3} \end{array}} \right]$ c) See image below.

Work Step by Step

a) Take the standard basis for $R^2,$ which is $\{(1,0),(0,1)\}=\{e_1,e_2\}$. We are given $T(x,y)=(-x,y)$ Then, $T(1,0)=(-1,0)\\ T(0,1)=(0,1)$ Therefore, the matrix corresponding to linear transformation $T$ is given by: $A=[T(e_1)$ $T(e_2)]$ $=\left[ {\begin{array}{*{20}{c}} { -1}&{0}\\ 0&{ 1} \end{array}} \right]$ b) Hence, the image of $v=\left[ {\begin{array}{*{20}{c}} 2\\ {-3} \end{array}} \right]$ is $\begin{array}{l} T(v) = Av\\ \Rightarrow T\left[ {\begin{array}{*{20}{c}} 2\\ {-3} \end{array}} \right] = \left[ {\begin{array}{*{20}{c}} { -1}&0\\ 0&1 \end{array}} \right]\left[ {\begin{array}{*{20}{c}} 2\\ {-3} \end{array}} \right] = \left[ {\begin{array}{*{20}{c}} { -2}\\ { -3} \end{array}} \right] \end{array}$ c)
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