Intermediate Algebra: Connecting Concepts through Application

Published by Brooks Cole
ISBN 10: 0-53449-636-9
ISBN 13: 978-0-53449-636-4

Appendix B - Matrices - B Exercises - Page B-15: 33

Answer

$(x,y,z)=(\frac{9}{2},\frac{5}{2},-2)$.

Work Step by Step

The augmented matrix is $\begin{bmatrix} 1&-1 &0 & 2\\ 0 & 2 & 1 & 3\\ 0& 0 & 1 & -2 \end{bmatrix}$. For the linear equation. First column $=$ coefficients of $x$. Second column $=$ coefficients of $y$ Third column $=$ coefficients of $z$ and fourth column $=$ the right-hand side. The given matrix is a upper triangular form. Rewrite the third row as a linear equation. $\Rightarrow 0x+0y+1z=-2$ $\Rightarrow z=-2$ Rewrite the second row as a linear equation. $\Rightarrow 0x+2y+z=3$ $\Rightarrow 2y+z=3$ Substitute $z=-2$. $\Rightarrow 2y+(-2)=3$ Clear the parentheses. $\Rightarrow 2y-2=3$ Add $2$ to both sides. $\Rightarrow 2y-2+2=3+2$ Simplify. $\Rightarrow 2y=5$ Divide both sides by $2$. $\Rightarrow \frac{2y}{2}=\frac{5}{2}$ Simplify. $\Rightarrow y=\frac{5}{2}$ Rewrite the first row as a linear equation. $\Rightarrow 1x-1y+0z=2$ $\Rightarrow x-y=2$ Substitute $y=\frac{5}{2}$. $\Rightarrow x-\frac{5}{2}=2$ Add $\frac{5}{2}$ to both sides. $\Rightarrow x-\frac{5}{2}+\frac{5}{2}=2+\frac{5}{2}$ Simplify. $\Rightarrow x=\frac{4+5}{2}$ $\Rightarrow x=\frac{9}{2}$ The solution set is $(x,y,z)=(\frac{9}{2},\frac{5}{2},-2)$.
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