Intermediate Algebra: Connecting Concepts through Application

Published by Brooks Cole
ISBN 10: 0-53449-636-9
ISBN 13: 978-0-53449-636-4

Chapter 1-8 - Cumulative Review - Page 678: 22

Answer

$(x,y) =\left(2, 2\right) $

Work Step by Step

Give $$\begin{cases} x&=4 y-6 \\ \frac{1}{2} x+6 y&=13. \end{cases}$$ Write $x$ as a function of $y$ for the second function. \begin{equation} \begin{aligned} x&=4 y-6\\ \left(\frac{1}{2} x+6 y\right)\cdot 2&=13\cdot 2\\ x+12y&= 26\\ x&= -12y+26. \end{aligned} \end{equation} Substitute the expression for the first equation into the second and solve for $y$. \begin{equation} \begin{aligned} 4y-6&=-12y+26\\ 4y+12y&=26+6\\ 16y &= 32\\ y&= \frac{32}{16}\\ &= 2.\\ x&=4\cdot (2)-6\\ & = 2. \end{aligned} \end{equation} The solution set is $(x,y) =\left(2, 2\right) $ Check \begin{equation} \begin{aligned} 2&\stackrel{?}{=}4 \cdot 2-6\\ 2&= 2\ \checkmark\\ \end{aligned} \end{equation}
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