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: 38

Answer

$\begin{bmatrix} x \\ y \end{bmatrix}= \begin{bmatrix} 3 \\ -5 \end{bmatrix} $

Work Step by Step

We will write the system of equations as follows: $\begin{bmatrix} 1 & 3 \\ 2 & -1 \end{bmatrix} \begin{bmatrix} x \\ y \end{bmatrix}=\begin{bmatrix} -12 \\ 11 \end{bmatrix} $ Next, we will find the inverse of the left matrix factor as follows: $\dfrac{1}{(1)(-1)-(3)(2)}\begin{bmatrix} -1 & -3 \\ -2 & 1 \end{bmatrix} $ This yields to: $\begin{bmatrix} 1/7 & 3/7 \\ 2/7 & -1/7 \end{bmatrix} $ Therefore, the value of $x,y$ can be calculated as: $\begin{bmatrix} x \\ y \end{bmatrix}=\begin{bmatrix} 1/7 & 3/7 \\ 2/7 & -1/7 \end{bmatrix} \begin{bmatrix} -12 \\ 11 \end{bmatrix} $ After matrix multiplication, we get:, $\begin{bmatrix} x \\ y \end{bmatrix}=\begin{bmatrix} 1/7 (-12) + (3/7)(11) \\ 2/7 (-12)-(1/7)(11) \end{bmatrix} = \begin{bmatrix} 3 \\ -5 \end{bmatrix} $ Hence, our result is: $\begin{bmatrix} x \\ y \end{bmatrix}= \begin{bmatrix} 3 \\ -5 \end{bmatrix} $
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.