Linear Algebra and Its Applications (5th Edition)

Published by Pearson
ISBN 10: 032198238X
ISBN 13: 978-0-32198-238-4

Chapter 1 - Linear Equations in Linear Algebra - 1.9 Exercises - Page 79: 19

Answer

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Work Step by Step

\[ T\left(x_{1}, x_{2}, x_{3}\right)=\left(x_{1}-5 x_{2}+4 x_{3}, x_{2}-6 x_{3}\right) \] Goal Show that $T$ is a linear transformation by finding a a matrix that implements the mapping. Concepts Definition of $A \mathbf{x}$ Solve $\begin{aligned} T(\mathbf{x}) &=T\left(x_{1}, x_{2}, x_{3}\right) \\ &=\left[\begin{array}{c}x_{1}-5 x_{2}+4 x_{3} \\ x_{2}-6 x_{3}\end{array}\right] \\ &=\left[\begin{array}{c}x_{1} \\ 0 x_{1}\end{array}\right]+\left[\begin{array}{c}-5 x_{2} \\ x_{2}\end{array}\right]+\left[\begin{array}{c}4 x_{3} \\ 6 x_{3}\end{array}\right] \\=& x_{1}\left[\begin{array}{c}1 \\ 0\end{array}\right]+x_{2}\left[\begin{array}{c}-5 \\ 1\end{array}\right]+x_{3}\left[\begin{array}{c}4 \\ -6\end{array}\right] \\=&\left[\begin{array}{ccc}1 & -5 & 4 \\ 0 & 1 & -6\end{array}\right]\left[\begin{array}{c}x_{1} \\ x_{2}\end{array}\right] \\=& A(\mathbf{x}) \end{aligned}$ Conclusion $A=\left[\begin{array}{ccc}1 & -5 & 4 \\ 0 & 1 & -6\end{array}\right]$
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