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: 45

Answer

The linear system of equations is: \[\begin{align} & y=x-4 \\ & y=-\frac{1}{3}x+4 \end{align}\]

Work Step by Step

Since the solution set is\[\left\{ \left( 6,2 \right) \right\}\], it implies the two equations intersect at the point\[\left( 6,2 \right)\]. According to the given graph the equations that intersect at\[\left( 6,2 \right)\]are, \[\begin{align} & x-y=4 \\ & x+3y=12 \end{align}\] Solve the above equations to verify. Subtract the two equations as follows: \[\underline{\begin{align} & x-y=4 \\ & -x-3y=-12 \end{align}}\] \[\begin{align} & \ \ \ \ \ \ -4y=-8 \\ & y=2 \end{align}\] Put \[y=2\]in any equation to get, \[\begin{align} & x-2=4 \\ & x=6 \end{align}\] To verify put\[y=2\]and\[x=6\]in\[x+3y=12\]as follows: \[\begin{align} & 6+3\left( 2 \right)=12 \\ & 6+6=12 \\ & 12=12 \end{align}\] RHS\[=\]LHS Hence verified. Hence, the linear system of equations is: \[\begin{align} & y=x-4 \\ & y=-\frac{1}{3}x+4 \end{align}\] With the solution set as\[\left\{ \left( 6,2 \right) \right\}\].
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