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: 42

Answer

The system of linear equations has only one solution and the solution set is\[\left\{ \left( 3,-2 \right) \right\}\].

Work Step by Step

Multiply \[5\]on both sides to the equation \[3x-y=11\]to get: \[15x-5y=55\]. Add the second given equation to the above-obtained equation from both RHS and LHS as follows: \[\underline{\begin{align} & 2x+5y=-4 \\ & 15x-5y=55 \end{align}}\] \[\begin{align} & 17x\ \ \ \ \ \ \ =51 \\ & x=3 \end{align}\] Put \[x=3\]in\[3x-y=11\], to get: \[\begin{align} & 3\left( 3 \right)-y=11 \\ & 9-y=11 \\ & -y=2 \\ & y=-2 \end{align}\] Put\[x=3\]and \[y=-2\]in any of the provided equations to check the solution, \[\begin{align} & 2\left( 3 \right)+5\left( -2 \right)=-4 \\ & 6-10=-4 \\ & -4=-4 \end{align}\] Since RHS\[=\]LHS, it implies the solution is correct. Hence the set \[\left\{ \left( 3,-2 \right) \right\}\]is the solution set of the provided system of linear equations.
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