Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 7 - Algebra: Graphs, Functions, and Linear Systems - 7.3 Systems of Linear Equations in Two Variables - Exercise Set 7.3 - Page 445: 47

Answer

The solution set is\[\left\{ \left( \frac{1}{a},3 \right),a\ne 0 \right\}\].

Work Step by Step

Multiply \[5\]on both sides to the equation \[ax+7y=22\]to get: \[5ax+35y=110\]. Subtract the second given equation to the above obtained equation from both RHS and LHS as follows: \[\underline{\begin{align} & 5ax+35y=110 \\ & -5ax-4y=-17 \end{align}}\] \[\begin{align} & \ \ \ \ \ \ \ \ \ \ 31y=93 \\ & y=3 \end{align}\] Put \[y=3\]in\[ax+7y=22\] to get: \[\begin{align} & ax+7\left( 3 \right)=22 \\ & ax+21=22 \\ & ax=1 \\ & x=\frac{1}{a},\ \ \ \ \ \ \ \ \ \ a\ne 0 \end{align}\] To verify put\[y=3\]and \[x=\frac{1}{a}\] in\[5ax+4y=17\] as follows: \[\begin{align} & 5a\left( \frac{1}{a} \right)+4\left( 3 \right)=17 \\ & 5+12=17 \\ & 17=17 \end{align}\] Since RHS\[=\]LHS Hence verified. Hence, the solution set is, \[\left\{ \left( \frac{1}{a},3 \right),a\ne 0 \right\}\].
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