Big Ideas Math - Algebra 1, A Common Core Curriculum

Published by Big Ideas Learning LLC
ISBN 10: 978-1-60840-838-2
ISBN 13: 978-1-60840-838-2

Chapter 5 - Solving Systems of Linear Equations - 5.2 - Solving Systems of Linear Equations by Substitution - Monitoring Progress - Page 243: 7

Answer

$(-2,-\frac{9}{2})$

Work Step by Step

The given system of equations is $\Rightarrow x-2y=7$ ...... (1) $\Rightarrow 3x-2y=3$ ...... (2) Solve for $x$ in equation (1). $\Rightarrow x-2y=7$ $\Rightarrow x=7+2y$ ...... (3) Substitute $7+2y$ for $x$ in equation (2). $\Rightarrow 3(7+2y)-2y=3$ Clear the parentheses. $\Rightarrow 21+6y-2y=3$ Add like terms. $\Rightarrow 21+4y=3$ Subtract $21$ from each side. $\Rightarrow 21+4y-21=3-21$ Simplify. $\Rightarrow 4y=-18$ Divide each side by $4$ $\Rightarrow \frac{4y}{4}=\frac{-18}{4}$ Simplify. $\Rightarrow y=-\frac{9}{2}$ Substitute $-\frac{9}{2}$ for $y$ in equation (3). $\Rightarrow x=7+2(-\frac{9}{2})$ Clear the parentheses. $\Rightarrow x=7-9$ Simplify. $\Rightarrow x=-2$ Check Equation (1) $\Rightarrow x-2y=7$ $\Rightarrow -2-2(-\frac{9}{2})=7$ $\Rightarrow -2+9=7$ $\Rightarrow 7=7$ True. Check Equation (2) $\Rightarrow 3x-2y=3$ $\Rightarrow 3(-2)-2(-\frac{9}{2})=3$ $\Rightarrow -6+9=3$ $\Rightarrow 3=3$ True. Hence, the solution is $(-2,-\frac{9}{2})$.
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