Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 3 - Section 3.1 - Systems of Linear Equations in Two Variables - Exercise Set - Page 193: 104

Answer

$(3,-2)$.

Work Step by Step

The given equations are $\Rightarrow 5x+8y=-1$ ...... (1) $\Rightarrow 3x+y=7$ ...... (2) Multiply the second equation by $-8$. $\Rightarrow -8\cdot (3x+y)=-8\cdot (7)$ Use distributive property. $\Rightarrow -24x-8y=-56$ ......(3) Add equation (1) and (3). $5x+8y-24x-8y=-1-56$ Add like terms. $-19x=-57$ Divide both sides by $-19$. $\frac{-19x}{-19}=\frac{-57}{-19}$ Simplify. $x=3$ Substitute the value of $x$ into equation (2). $\Rightarrow 3(3)+y=7$ Clear the parentheses. $\Rightarrow 9+y=7$ Subtract $9$ from both sides. $\Rightarrow 9+y-9=7-9$ Simplify. $\Rightarrow y=-2$ Plug $(x,y)=(3,-2)$ into equation (2). $\Rightarrow 3(3)+(-2)=7$ $\Rightarrow 9-2=7$ $\Rightarrow 7=7$ True. Solution set is $(3,-2)$.
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