College Algebra (6th Edition)

Published by Pearson
ISBN 10: 0-32178-228-3
ISBN 13: 978-0-32178-228-1

Chapter 6 - Summary, Review, and Test - Review Exercises - Page 656: 27

Answer

$\begin{bmatrix} -6&-22&-40\\9&43&58\\-14&-48&-94\end{bmatrix}$

Work Step by Step

We are given the matrices: $A=\begin{bmatrix} 2&-1&2\\5&3&-1\end{bmatrix}$ $B=\begin{bmatrix} 0&-2\\3&2\\1&-5\end{bmatrix}$ $C=\begin{bmatrix} 1&2&3\\-1&1&2\\-1&2&1\end{bmatrix}$ Compute $B(AC)$: $B(AC)=\begin{bmatrix} 0&-2\\3&2\\1&-5\end{bmatrix}\left(\begin{bmatrix} 2&-1&2\\5&3&-1\end{bmatrix}\begin{bmatrix} 1&2&3\\-1&1&2\\-1&2&1\end{bmatrix}\right)$ $=\begin{bmatrix} 0&-2\\3&2\\1&-5\end{bmatrix}\begin{bmatrix} 2+1-2&4-1+4&6-2+2\\5-3+1&10+3-2&15+6-1\end{bmatrix}$ $=\begin{bmatrix} 0&-2\\3&2\\1&-5\end{bmatrix}\begin{bmatrix}1&7&6\\3&11&20\end{bmatrix}$ $=\begin{bmatrix} 0-6&0-22&0-40\\3+6&21+22&18+40\\1-15&7-55&6-100\end{bmatrix}$ $=\begin{bmatrix} -6&-22&-40\\9&43&58\\-14&-48&-94\end{bmatrix}$
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