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 - Exercises - Page 245: 10

Answer

The solution is $(1,-3)$.

Work Step by Step

The given system of equations is $\Rightarrow 6x-9=y$ ...... (1) $\Rightarrow y=-3x$ ...... (2) Substitute $-3x$ for $y$ in equation (1). $\Rightarrow 6x-9=-3x$ Add $3x+9$ to each side. $\Rightarrow 6x-9+3x+9=-3x+3x+9$ Simplify. $\Rightarrow 9x=9$ Divide each side by $9$. $\Rightarrow \frac{9x}{9}=\frac{9}{9}$ Simplify. $\Rightarrow x=1$ Substitute $1$ for $x$ in equation (2). $\Rightarrow y=-3(1)$ Simplify. $\Rightarrow y=-3$ Check Equation (1) $\Rightarrow 6x-9=y$ $\Rightarrow 6(1)-9=-3$ $\Rightarrow 6-9=-3$ $\Rightarrow -3=-3$ True. Check Equation (2) $\Rightarrow y=-3x$ $\Rightarrow -3=-3(1)$ $\Rightarrow -3=-3$ True. Hence, the solution is $(1,-3)$.
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