Elementary Technical Mathematics

Published by Brooks Cole
ISBN 10: 1285199197
ISBN 13: 978-1-28519-919-1

Chapter 9 - Section 9.2 - Solving Pairs of Linear Equations by Addition - Exercises - Page 332: 44


One common solution $\Rightarrow$ $(4,-1)$

Work Step by Step

We use the addition method below: We add the two equations: $2x-5y=13$ $5x+7y=13$ Multiply the first equation by $5$ and the second equation by $-2$ to cancel $x$: $+10x-25y=+65$ $\underline{-10x-14y=-26}$ $-39y=39$ Solve for $y$: $y=\frac{39}{-39}=-1$ Substitute into any of the two equations and solve for $x$: $2x-5y=13$ $2x-5(-1)=13$ $2x+5=13$ $2x=13-5$ $2x=8$ $x=\frac{8}{2}$ $x=4$
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