Algebra 2 Common Core

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

Chapter 12 - Matrices - 12-3 Determinants and Inverses - Practice and Problem-Solving Exercises - Page 790: 67

Answer

$X = \begin{bmatrix} 2 & 5 \\ 1 & 1 \end{bmatrix}$

Work Step by Step

Using the properties of matrices, the given matrix equation, $ 2\begin{bmatrix} -1 & 3 \\ -2 & 0 \end{bmatrix} -3X = \begin{bmatrix} -8 & -9 \\ -7 & -3 \end{bmatrix} ,$ is equivalent to \begin{align*}\require{cancel} \begin{bmatrix} -1(2) & 3(2) \\ -2(2) & 0(2) \end{bmatrix} -3X &= \begin{bmatrix} -8 & -9 \\ -7 & -3 \end{bmatrix} \\\\ \begin{bmatrix} -2 & 6 \\ -4 & 0 \end{bmatrix} -3X &= \begin{bmatrix} -8 & -9 \\ -7 & -3 \end{bmatrix} \\\\ -3X &= \begin{bmatrix} -8 & -9 \\ -7 & -3 \end{bmatrix} -\begin{bmatrix} -2 & 6 \\ -4 & 0 \end{bmatrix} \\\\ -3X &= \begin{bmatrix} -8-(-2) & -9-6 \\ -7-(-4) & -3-0 \end{bmatrix} \\\\ -3X &= \begin{bmatrix} -8+2 & -9-6 \\ -7+4 & -3-0 \end{bmatrix} \\\\ -3X &= \begin{bmatrix} -6 & -15 \\ -3 & -3 \end{bmatrix} \\\\ \left(-\dfrac{1}{3}\right)(-3X) &= -\dfrac{1}{3}\begin{bmatrix} -6 & -15 \\ -3 & -3 \end{bmatrix} \\\\ X &= \begin{bmatrix} -6\left(-\dfrac{1}{3}\right) & -15\left(-\dfrac{1}{3}\right) \\ -3\left(-\dfrac{1}{3}\right) & -3\left(-\dfrac{1}{3}\right) \end{bmatrix} \\\\ X &= \begin{bmatrix} 2 & 5 \\ 1 & 1 \end{bmatrix} .\end{align*} Hence, the solution is $ X = \begin{bmatrix} 2 & 5 \\ 1 & 1 \end{bmatrix} .$
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