Algebra 2 Common Core

Published by Prentice Hall
ISBN 10: 0133186024
ISBN 13: 978-0-13318-602-4

Chapter 12 - Matrices - 12-2 Matrix Multiplication - Practice and Problem-Solving Exercises - Page 777: 14

Answer

$2A-5B=\begin{bmatrix} 21 & 3 \\ 2 & 16 \\ 7 & -25 \end{bmatrix}$

Work Step by Step

Multiplying each element of $A= \begin{bmatrix} 3 & 4 \\ 6 & -2 \\ 1 & 0 \end{bmatrix} $ by $2,$ and then subtracting the result to $5$ times each element of $B= \begin{bmatrix} -3 & 1 \\ 2 & -4 \\ -1 & 5 \end{bmatrix} ,$ then \begin{align*} 2A-5B&= \begin{bmatrix} 3(2) & 4(2) \\ 6(2) & -2(2) \\ 1(2) & 0(2) \end{bmatrix} - \begin{bmatrix} -3(5) & 1(5) \\ 2(5) & -4(5) \\ -1(5) & 5(5) \end{bmatrix} \\\\&= \begin{bmatrix} 6 & 8 \\ 12 & -4 \\ 2 & 0 \end{bmatrix} - \begin{bmatrix} -15 & 5 \\ 10 & -20 \\ -5 & 25 \end{bmatrix} \\\\&= \begin{bmatrix} 6-(-15) & 8-5 \\ 12-10 & -4-(-20) \\ 2-(-5) & 0-25 \end{bmatrix} \\\\&= \begin{bmatrix} 6+15 & 8-5 \\ 12-10 & -4+20 \\ 2+5 & 0-25 \end{bmatrix} \\\\&= \begin{bmatrix} 21 & 3 \\ 2 & 16 \\ 7 & -25 \end{bmatrix} .\end{align*} Hence, $ 2A-5B=\begin{bmatrix} 21 & 3 \\ 2 & 16 \\ 7 & -25 \end{bmatrix} .$
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