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 - 5.3 - Solving Systems of Linear Equations by Elimination - Monitoring Progress - Page 249: 1

Answer

The solution is $(1,2)$.

Work Step by Step

The given system of equations is $3x+2y=7$ ...... (1) $-3x+4y=5$ ...... (2) Add equation (1) and (2). $\Rightarrow 3x+2y-3x+4y=7+5$ Add like terms. $\Rightarrow 6y=12$ Divide each side by $6$. $\Rightarrow \frac{6y}{6}=\frac{12}{6}$ Simplify. $\Rightarrow y=2$ Substitute $2$ for $y$ equation (1). $\Rightarrow 3x+2(2)=7$ Simplify. $\Rightarrow 3x+4=7$ Subtract $4$ from each side. $\Rightarrow 3x+4-4=7-4$ Simplify. $\Rightarrow 3x=3$ Divide each side by $3$. $\Rightarrow \frac{3x}{3}=\frac{3}{3}$ Simplify. $\Rightarrow x=1$. Check (x,y)=(1,2) Equation (1): $\Rightarrow 3x+2y=7$ $\Rightarrow 3(1)+2(2)=7$ $\Rightarrow 3+4=7$ $\Rightarrow 7=7$ True. Equation (2): $\Rightarrow -3x+4y=5$ $\Rightarrow -3(1)+4(2)=5$ $\Rightarrow -3+8=5$ $\Rightarrow 5=5$ True. Hence, the solution is $(1,2)$.
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