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: 21


One common solution $\Rightarrow$ $(-2,5)$

Work Step by Step

We use the addition method below: We add the 2 equations: $8x-7y=-51$ $12x+13y=41$ We multiply the first equation by $3$ and the second by $-2$ to cancel $x$: $+24x-21y=-153$ $\underline{-24x-26y=-82}$ $-47y=-235$ Solve for $y$: $y=\frac{-235}{-47}=5$ Substitute into any of the 2 equations and solve for $x$: $8x-7y=-51$ $8x-7(5)=-51$ $8x-35=-51$ $8x=-51+35$ $8x=-16$ $x=\frac{-16}{8}$ $x=-2$
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