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: 43


One common solution $\Rightarrow$ $(9,-2)$

Work Step by Step

We use the addition method below: We add the two equations: $7x+8y=47$ $5x-3y=51$ Multiply the first equation by $5$ and the second equation by $-7$ to cancel $x$: $+35x+40y=+235$ $\underline{-35x+21y=-357}$ $61y=-122$ Solve for $y$: $y=\frac{-122}{61}=-2$ Substitute into any of the two equations and solve for $x$: $7x+8y=47$ $7x+8(-2)=47$ $7x-16=47$ $7x=47+16$ $7x=63$ $x=\frac{63}{7}$ $x=9$
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