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: 29

Answer

$(x,y)=(\frac{7}{3},-2)$.

Work Step by Step

The augmented matrix is $\begin{bmatrix} 3&1 &5 \\ 0 & 2 & -4 \end{bmatrix}$. For the linear equation. First column $=$ coefficients of $x$. Second column $=$ coefficients of $y$ and third column $=$ the right-hand side. The given matrix is a upper triangular form. Rewrite the second row as a linear equation. $\Rightarrow 0x+2y=-4$ $\Rightarrow 2y=-4$ Divide the equation by $2$. $\Rightarrow \frac{2y}{2}=\frac{-4}{2}$ Simplify. $\Rightarrow y=-2$ Rewrite the first row as a linear equation. $\Rightarrow 3x+1y=5$ $\Rightarrow 3x+y=5$ Substitute $y=-2$. $\Rightarrow 3x+(-2)=5$ Clear the parentheses. $\Rightarrow 3x-2=5$ Add $2$ to both sides. $\Rightarrow 3x-2+2=5+2$ Simplify. $\Rightarrow 3x=7$ Divide both sides by $3$. $\Rightarrow \frac{3x}{3}=\frac{7}{3}$ Simplify. $\Rightarrow x=\frac{7}{3}$ The solution set is $(x,y)=(\frac{7}{3},-2)$.
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