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: 8

Answer

$$x_1=\frac{6}{7}, \quad x_2=-{\frac { 23}{7}}.$$

Work Step by Step

The system can written on the form $Ax=b$ as follows $$x_1\left[ \begin {array}{c} {2} \\{3} \end {array} \right]+x_2\left[ \begin {array}{c} {-1}\\ {2} \end {array} \right]=\left[ \begin {array}{c} {5}\\ {-4} \end {array} \right].$$ To solve system using Gaussian elimination, we form the augmented matrix as follows $$\left[ \begin {array}{ccc} 2&-1&5\\ 3&2&-4 \end {array} \right] . $$ The reduced row echelon form is given by $$\left[ \begin {array}{ccc} 1&0&\frac{6}{7}\\ 0&1&-{\frac { 23}{7}}\end {array} \right] . $$ From which, we have $$x_1=\frac{6}{7}, \quad x_2=-{\frac { 23}{7}}.$$
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