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 - Exercises - Page 251: 9

Answer

The solution is $(0,-10)$.

Work Step by Step

The given system of equations is $-y-10=6x$ ...... (1) $5x+y=-10$ ...... (2) Add equation (1) and (2). $\Rightarrow -y-10+5x+y=6x-10$ Add like terms. $\Rightarrow -10+5x=6x-10$ Add $-5x+10$ to each side. $\Rightarrow -10+5x-5x+10=6x-10-5x+10$ Simplify. $\Rightarrow 0=x$ Substitute $0$ for $x$ in equation (2). $\Rightarrow 5(0)+y=-10$ Simplify. $\Rightarrow 0+y=-10$ $\Rightarrow y=-10$ Check $(x,y)=(0,-10)$ Equation (1): $\Rightarrow -y-10=6x$ $\Rightarrow -(-10)-10=6(0)$ $\Rightarrow 10-10=0$ $\Rightarrow 0=0$ True. Equation (2): $\Rightarrow 5x+y=-10$ $\Rightarrow 5(0)-10=-10$ $\Rightarrow 0-10=-10$ $\Rightarrow -10=-10$ True. Hence, the solution is $(0,-10)$.
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