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 - Chapter Review - Page 283: 8

Answer

The solution is $(2,-8)$.

Work Step by Step

The given system of equations is $9x-2y=34$ ...... (1) $5x+2y=-6$ ...... (2) Add equation (1) and (2). $\Rightarrow 9x-2y+5x+2y=34-6$ Add like terms. $\Rightarrow 14x=28$ Divide each side by $14$. $\Rightarrow \frac{14x}{14}=\frac{28}{14}$ Simplify. $\Rightarrow x=2$ Substitute $2$ for $x$ in equation (2). $\Rightarrow 5(2)+2y=-6$ Simplify. $\Rightarrow 10+2y=-6$ Subtract $10$ from each side. $\Rightarrow 10+2y-10=-6-10$ Simplify. $\Rightarrow 2y=-16$ Divide each side by $2$. $\Rightarrow \frac{2y}{2}=-\frac{16}{2}$ Simplify. $\Rightarrow y=-8$ Check $(x,y)=(2,-8)$ Equation (1): $\Rightarrow 9x-2y=34$ $\Rightarrow 9(2)-2(-8)=34$ $\Rightarrow 18+16=34$ $\Rightarrow 34=34$ True. Equation (2): $\Rightarrow 5x+2y=-6$ $\Rightarrow 5(2)+2(-8)=-6$ $\Rightarrow 10-16=-6$ $\Rightarrow -6=-6$ True. Hence, the solution is $(2,-8)$.
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