Intermediate Algebra (12th Edition)

Published by Pearson
ISBN 10: 0321969359
ISBN 13: 978-0-32196-935-4

Chapter 8 - Chapter R-8 - Cumulative Review Exercises - Page 578: 16

Answer

a) $y=-\dfrac{5}{2}x+2$ b) $y=\dfrac{2}{5}x+\dfrac{13}{5}$

Work Step by Step

a) In the form $y=mx+b$, the given equation $ 5x+2y=6 ,$ is equivalent to \begin{align*}\require{cancel} 2y&=-5x+6 \\\\ \dfrac{\cancel2y}{\cancel2}&=\dfrac{-5x+6}{2} \\\\ y&=\dfrac{-5}{2}x+\dfrac{6}{2} \\\\ y&=-\dfrac{5}{2}x+3 .\end{align*} Since the slope of $y=mx+b$ is given by $m$, then the slope of the line in the equation above is $-\dfrac{5}{2}$. Since parallel lines have the same slope, then the slope of the required line is $m=-\dfrac{5}{2}$. Using $y-y_1=m(x-x_1)$ or the Point-Slope Form of linear equations, with $(x_1,y_1)=(2,-3),$ then \begin{align*} y-(-3)&=-\dfrac{5}{2}(x-2) \\\\ y+3&=-\dfrac{5}{2}(x-2) .\end{align*} In the form $y=mx+b,$ the equation above is equivalent to \begin{align*} y+3&=-\dfrac{5}{2}x+5 \\\\ y&=-\dfrac{5}{2}x+5-3 \\\\ y&=-\dfrac{5}{2}x+2 .\end{align*} Hence, the equation of the required line is $ y=-\dfrac{5}{2}x+2 $. b) In the form $y=mx+b$, the given equation $ 5x+2y=6 ,$ is equivalent to \begin{align*}\require{cancel} 2y&=-5x+6 \\\\ \dfrac{\cancel2y}{\cancel2}&=\dfrac{-5x+6}{2} \\\\ y&=\dfrac{-5}{2}x+\dfrac{6}{2} \\\\ y&=-\dfrac{5}{2}x+3 .\end{align*} Since the slope of $y=mx+b$ is given by $m$, then the slope of the line in the equation above is $-\dfrac{5}{2}$. Since perpendicular lines have negative reciprocal slopes, then the slope of the required line is $m=\dfrac{2}{5}$. Using $y-y_1=m(x-x_1)$ or the Point-Slope Form of linear equations, with $(x_1,y_1)=(-4,1),$ then \begin{align*} y-1&=\dfrac{2}{5}(x-(-4)) \\\\ y-1&=\dfrac{2}{5}(x+4) .\end{align*} In the form $y=mx+b,$ the equation above is equivalent to \begin{align*} y-1&=\dfrac{2}{5}(x)+\dfrac{2}{5}(4) \\\\ y-1&=\dfrac{2}{5}x+\dfrac{8}{5} \\\\ y&=\dfrac{2}{5}x+\dfrac{8}{5}+1 \\\\ y&=\dfrac{2}{5}x+\dfrac{8}{5}+\dfrac{5}{5} \\\\ y&=\dfrac{2}{5}x+\dfrac{13}{5} .\end{align*} Hence, the equation of the required line is $ y=\dfrac{2}{5}x+\dfrac{13}{5} $.
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