Algebra: A Combined Approach (4th Edition)

Published by Pearson
ISBN 10: 0321726391
ISBN 13: 978-0-32172-639-1

Chapter 10 - Cumulative Review - Page 754: 33

Answer

$x=3$ and $y=1$

Work Step by Step

Given the equations $3x+4y=13$ and $5x-9y=6$, $3x+4y=13 \rightarrow 4y=13-3x \rightarrow y=\dfrac{13-3x}{4}$ $5x-9y=6 \rightarrow -9y=6-5x \rightarrow y=\dfrac{6-5x}{-9}.$ Matching equations, we have $\dfrac{13-3x}{4} = \dfrac{6-5x}{-9} \rightarrow -9(13-3x) = 4(6-5x) \rightarrow -117+27x = 24-20x \rightarrow 27x+20x = 24+117 \rightarrow 47x = 141 \rightarrow x = \dfrac{141}{47} = 3$. Substituting $x$, we have $y=\dfrac{13-3x}{4} = \dfrac{13-3(3)}{4} = \dfrac{13-9}{4} = \dfrac{4}{4} = 1$. Therefore $x=3$ and $y=1$.
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