College Algebra (11th Edition)

Published by Pearson
ISBN 10: 0321671791
ISBN 13: 978-0-32167-179-0

Chapter 5 - Section 5.8 - Matrix Inverses - 5.8 Exercises - Page 567: 37

Answer

$\begin{bmatrix} x \\ y \end{bmatrix}= \begin{bmatrix} -2 \\ 4 \end{bmatrix} $

Work Step by Step

We will write the system of equations as follows: $\begin{bmatrix} 2 & -1 \\ 3 & 1 \end{bmatrix} \begin{bmatrix} x \\ y \end{bmatrix}=\begin{bmatrix} -8 \\ -2 \end{bmatrix} $ Next, we will find the inverse of the left matrix factor as follows: $\dfrac{1}{(2)(1)+(1)(3)}\begin{bmatrix} 1 & 1 \\ -3 & 2 \end{bmatrix} $ This yields to: $\begin{bmatrix} 1/5 & 1/5 \\ -3/5 & 2/5 \end{bmatrix} $ Therefore, the value of $x,y$ can be calculated as: $\begin{bmatrix} x \\ y \end{bmatrix}=\begin{bmatrix} 1/5 & 1/5 \\ -3/5 & 2/5 \end{bmatrix} \begin{bmatrix} -8 \\ -2 \end{bmatrix} $ After matrix multiplication, we get:, $\begin{bmatrix} x \\ y \end{bmatrix}=\begin{bmatrix} -2 \\ 4 \end{bmatrix} $ Hence, our result is: $\begin{bmatrix} x \\ y \end{bmatrix}= \begin{bmatrix} -2 \\ 4 \end{bmatrix} $
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