Intermediate Algebra (12th Edition)

Published by Pearson
ISBN 10: 0321969359
ISBN 13: 978-0-32196-935-4

Chapter 9 - Chapter R-9 - Cumulative Review Exercises - Page 642: 14

Answer

$\{(4,2)\}$

Work Step by Step

Multiplying the first equation by $5$ and the second equation by $3$, the given system, $ \begin{array}{l} 5x-3y=14 \\ 2x+5y=18 \end{array}$, is equivalent to \begin{align*}\require{cancel} 25x-15y&=70 \\ 6x+15y&=54 .\end{align*} Adding the two equations above and solving for the variable result to \begin{align*}\require{cancel} 31x&=124 \\\\ \dfrac{\cancel{31}x}{\cancel{31}}&=\dfrac{124}{31} \\\\ x&=4 .\end{align*} Substituting $x=4$ in the first equation, $ 5x-3y=14 $, results to \begin{align*}\require{cancel} 5(4)-3y&=14 \\ 20-3y&=14 \\ 20-14&=3y \\ 6&=3y \\\\ \dfrac{6}{3}&=\dfrac{\cancel3y}{\cancel3} \\\\ 2&=y .\end{align*} Hence, the solution set of the system $\begin{array}{l} 5x-3y=14 \\ 2x+5y=18 \end{array}$ is $ \{(4,2)\} $.
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