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 1 - Solving Linear Equations - 1.4 - Solving Absolute Value Equations - Exercises - Page 33: 36

Answer

The solutions are $c=1$ and $c=-\frac{2}{3}$.

Work Step by Step

The given equation is $\Rightarrow |2c+8|=|10c|$ Write the two related linear equations. $2c+8=10c$ ...... (1) $2c+8=-10c$ ...... (2) Solve equation (1). $\Rightarrow 2c+8=10c$ Subtract $2c$ from each side. $\Rightarrow 2c+8-2c=10c-2c$ Simplify. $\Rightarrow 8=8c$ Divide each side by $8$. $\Rightarrow \frac{8}{8}=\frac{8c}{8}$ Simplify. $\Rightarrow 1=c$ Check : $c=1$ $\Rightarrow |2c+8|=|10c|$ $\Rightarrow |2(1)+8|=|10(1)|$ $\Rightarrow |2+8|=|10|$ $\Rightarrow |10|=|10|$ True. Solve equation (2). $\Rightarrow 2c+8=-10c$ Add $10c-8$ to each side. $\Rightarrow 2c+8+10c-8=-10c+10c-8$ Simplify. $\Rightarrow 12c=-8$ Divide each side by $12$. $\Rightarrow \frac{12c}{12}=-\frac{8}{12}$ Simplify. $\Rightarrow c=-\frac{2}{3}$ Check : $c=-\frac{2}{3}$ $\Rightarrow |2c+8|=|10c|$ $\Rightarrow |2(-\frac{2}{3})+8|=|10(-\frac{2}{3})|$ $\Rightarrow |-\frac{4}{3}+8|=|\frac{20}{3}|$ $\Rightarrow |\frac{-4+24}{3}|=|\frac{20}{3}|$ $\Rightarrow |\frac{20}{3}|=|\frac{20}{3}|$ True. Hence, the solutions are $c=1$ and $c=-\frac{2}{3}$.
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