Elementary Linear Algebra 7th Edition

Published by Cengage Learning
ISBN 10: 1-13311-087-8
ISBN 13: 978-1-13311-087-3

Chapter 2 - Matrices - Review Exercises - Page 98: 23

Answer

$$x_1=10,\quad x_2= -12.$$

Work Step by Step

We have the system $$\left[ \begin {array}{ccc} 5&4\\ -1& 1 \end {array} \right] \left[\begin{array}{rrr}{x_1}\\ {x_2} \end{array}\right]=\left[\begin{array}{rrr}{2} \\ {-22} \end{array}\right].$$ The coefficients matrix $A= \left[ \begin {array}{ccc} 5&4\\ -1& 1 \end {array} \right] $ has the inverse $$A^{-1}=\left[ \begin {array}{cc} \frac{1}{9}&-\frac{4}{9}\\ \frac{1}{9}&\frac{5}{9} \end {array} \right] . $$ The system has the solution $$\left[\begin{array}{rrr}{x_1}\\ {x_2} \end{array}\right]=\left[ \begin {array}{cc} \frac{1}{9}&-\frac{4}{9}\\ \frac{1}{9}&\frac{5}{9} \end {array} \right]\left[\begin{array}{rrr}{2} \\ {-22} \end{array}\right]=\left[ \begin {array}{c} {10}\\ -12 \end {array} \right] .$$ That is $$x_1=10,\quad x_2= -12.$$
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.