Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Published by Pearson
ISBN 10: 0-32184-874-8
ISBN 13: 978-0-32184-874-1

Chapter 1-14 - Cumulative Review - Final Exam - Page 930: 38

Answer

$x=-1$ and $y=\dfrac{1}{2}$

Work Step by Step

To solve the given system, \begin{align*}\require{cancel} 5x+6y&=-2 \\ 3x+10y&=2 ,\end{align*} Cancel the $y$-variable by multiplying the first equation by $-5$ and the second equation by $3$. This results to the equivalent system \begin{align*}\require{cancel} &\left\{ \begin{array}{ll} (-5)(5x+6y)&=(-2)(-5) \\ (3)(3x+10y)&=(2)(3) \end{array} \right. \\\\& \left\{ \begin{array}{ll} -25x-30y&=10 \\ 9x+30y&=6 \end{array} \right. .\end{align*} Adding the two equations above and using the properties of equality to solve for the remaining variable result in \begin{align*} -16x&=16 \\\\ \dfrac{\cancel{-16}x}{\cancel{-16}}&=\dfrac{16}{-16} \\\\ x&=-1 .\end{align*} Substituting $x=-1$ in the first given equation, $5x+6y=-2,$ results in \begin{align*} 5(-1)+6y&=-2 \\ -5+6y&=-2 \\ -5+5+6y&=-2+5 \\ 6y&=3 \\\\ \dfrac{\cancel6y}{\cancel6}&=\dfrac{3}{6} \\\\ y&=\dfrac{1}{2} .\end{align*} Hence, the solution to the given system is $x=-1$ and $y=\dfrac{1}{2}$.
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