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: 38

Answer

The solutions are $k=6$ and $k=-\frac{2}{5}$.

Work Step by Step

The given equation is $\Rightarrow |3k-2|=2|k+2|$ Write the two related linear equations. $3k-2=2(k+2)$ ...... (1) $3k-2=2[-(k+2)]$ ...... (2) Solve equation (1). $\Rightarrow 3k-2=2(k+2)$ Use distributive property. $\Rightarrow 3k-2=2k+4$ Add $2-2k$ to each side. $\Rightarrow 3k-2+2-2k=2k+4+2-2k$ Simplify. $\Rightarrow k=6$ Check : $k=6$ $\Rightarrow |3k-2|=2|k+2|$ $\Rightarrow |3(6)-2|=2|6+2|$ $\Rightarrow |18-2|=2|8|$ $\Rightarrow |16|=2|8|$ $\Rightarrow 16=16$ True. Solve equation (2). $\Rightarrow 3k-2=2[-(k+2)]$ $\Rightarrow 3k-2=-2(k+2)$ Use distributive property. $\Rightarrow 3k-2=-2k-4$ Add $2+2k$ to each side. $\Rightarrow 3k-2+2+2k=-2k-4+2+2k$ Simplify. $\Rightarrow 5k=-2$ Divide each side by $5$. $\Rightarrow \frac{5k}{5}=-\frac{2}{5}$ Simplify. $\Rightarrow k=-\frac{2}{5}$ Check : $k=-\frac{2}{5}$ $\Rightarrow |3k-2|=2|k+2|$ $\Rightarrow |3(-\frac{2}{5})-2|=2|-\frac{2}{5}+2|$ $\Rightarrow |-\frac{6}{5}-2|=2|-\frac{2}{5}+2|$ $\Rightarrow |\frac{-6-10}{5}|=2|\frac{-2+10}{5}|$ $\Rightarrow |\frac{-16}{5}|=2|\frac{8}{5}|$ $\Rightarrow \frac{16}{5}=2(\frac{8}{5})$ $\Rightarrow \frac{16}{5}=\frac{16}{5}$ True. Hence, the solutions are $k=6$ and $k=-\frac{2}{5}$.
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