Algebra 2 (1st Edition)

Published by McDougal Littell
ISBN 10: 0618595414
ISBN 13: 978-0-61859-541-9

Chapter 3 Linear Systems and Matrices - Chapter Review - Page 226: 33

Answer

$x=7, y=1$

Work Step by Step

Write the linear system as a matrix equation $AX = B$. $\begin{bmatrix} 1 & 4 \\ 2 &-5 \end{bmatrix}\begin{bmatrix} x\\ y \end{bmatrix}=\begin{bmatrix} 11\\ 9 \end{bmatrix}$ Then multiply the matrix of constants by $A^{-1}$ on the left $\begin{bmatrix} x\\ y \end{bmatrix}=\frac{1}{-5-8}\begin{bmatrix} -5 & -4\\ -2 &1 \end{bmatrix}\begin{bmatrix} 11\\ 9 \end{bmatrix}$ $\begin{bmatrix} x\\ y \end{bmatrix}=\frac{-1}{13}\begin{bmatrix} -91\\ -13 \end{bmatrix}$ $\begin{bmatrix} x\\ y \end{bmatrix}=\begin{bmatrix} 7\\ 1 \end{bmatrix}$ Hence, $x=7, y=1$
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