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: 77

Answer

$ x=-4,y=2,z=\displaystyle \frac{5}{2}$ or $\displaystyle \left(-4,2,\frac{5}{2}\right)$

Work Step by Step

Method: Gauss-Jordan. Row reduce the augmented matrix: $\left[\begin{array}{rrr|r} 1 & -2 & 4 & 2 \\ -3 & 5 & -2 & 17 \\ 4 & -3 & 0 & -22 \end{array}\right]\qquad\left\{\begin{array}{l} .\\ R_{2}=r_{2}+3r_{1}.\\ R_{3}=r_{3}-4r_{1}. \end{array}\right\}\rightarrow$ $\rightarrow\left[\begin{array}{rrr|r} 1 & -2 & 4 & 2 \\ 0 & -1 & 10 & 23 \\ 0 & 5 & -16 & -30 \end{array}\right]\qquad\left\{\begin{array}{l} R_{1}=r_{1}-2r_{2}.\\ R_{2}=-r_{2}.\\ R_{3}=r_{3}+5r_{2}. \end{array}\right\}\rightarrow$ $\rightarrow\left[\begin{array}{rrr|r} 1 & 0 & -16 & -44 \\ 0 & 1 & -10 & -23 \\ 0 & 0 & 34 & 85 \end{array}\right]\qquad\left\{\begin{array}{l} .\\ .\\ R_{3}=r_{3}\div 34. \end{array}\right\}\rightarrow$ $\rightarrow\left[\begin{array}{rrr|r} 1 & 0 & -16 & -44 \\ 0 & 1 & -10 & -23 \\ 0 & 0 & 1 & 5/2 \end{array}\right]\qquad\left\{\begin{array}{l} R_{1}=r_{1}+16r_{3}.\\ R_{2}=r_{2}+10r_{3}.\\ . \end{array}\right\}\rightarrow$ $\rightarrow\left[\begin{array}{rrr|r} 1 & 0 & 0 & -4 \\ 0 & 1 & 0 & 2 \\ 0 & 0 & 1 & 5/2 \end{array}\right]$ Solution: $ x=-4,y=2,z=\displaystyle \frac{5}{2}$ or $\displaystyle \left(-4,2,\frac{5}{2}\right)$
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