College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 8 - Section 8.4 - Matrix Algebra - 8.4 Assess Your Understanding - Page 599: 75

Answer

$x=-5,\ y=7$ or $(-5,7)$

Work Step by Step

Method: Gauss-Jordan. Row reduce the augmented matrix: $\left[\begin{array}{rr|r} 2 & 3 & 11 \\ 5 & 7 & 24 \end{array}\right]\qquad\left\{\begin{array}{l} R_{1}=3r_{1}-r_{2}\\ . \end{array}\right\}\rightarrow$ $\rightarrow\left[\begin{array}{rr|r} 1 & 2 & 9 \\ 5 & 7 & 24 \end{array}\right]\qquad\left\{\begin{array}{l} .\\ R_{2}=r_{2}-5r_{1}. \end{array}\right\}\rightarrow$ $\rightarrow\left[\begin{array}{rr|r} 1 & 2 & 9 \\ 0 & -3 & -21 \end{array}\right]\qquad\left\{\begin{array}{l} .\\ R_{2}=-r_{2}\div 3. \end{array}\right\}\rightarrow$ $\rightarrow\left[\begin{array}{rr|r} 1 & 2 & 9 \\ 0 & 1 & 7 \end{array}\right]\qquad\left\{\begin{array}{l} R_{1}=r_{1}-2r_{2}.\\ . \end{array}\right\}\rightarrow$ $\rightarrow\left[\begin{array}{rr|r} 1 & 0 & -5 \\ 0 & 1 & 7 \end{array}\right]$ Solution: $x=-5,\ y=7$ or $(-5,7)$
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