College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 1, Equations and Graphs - Chapter 1 Review - Exercises - Page 170: 41

Answer

a) $y=\dfrac{2}{5}x+\dfrac{3}{5}$ b) $2x-5y+3=0$

Work Step by Step

a) The equation of a line in slope-intercept form is: $$y=mx+b,\tag1$$ where $m$ is the slope and $b$ in the $y$-intercept. We are given: $$\begin{align*} &\text{The line is parallel to the line }2x-5y=10\\ &P(1,1)\text{ belongs to the line}. \end{align*}$$ Because the line is parallel to the line $2x-5y=10$, it means they have the same slope. We determine that slope: $$\begin{align*} 2x-5y&=10\\ 5y&=2x-10\\ y&=\dfrac{2}{5}x-2\\ m&=\dfrac{2}{5}. \end{align*}$$ We substitute $m=2/5$ in Eq. $(1)$: $$y=\dfrac{2}{5}x+b.\tag2$$ Determine $b$ using the coordinates of the point $P$ in Eq. $(2)$: $$\begin{align*} 1&=\dfrac{2}{5}(1)+b\\ b&=1-\dfrac{2}{5}\\ b&=\dfrac{3}{5}. \end{align*}$$ The equation of the line is: $$y=\dfrac{2}{5}x+\dfrac{3}{5}.$$ b) The equation of a line in general form is: $$Ax+By+C=0.$$ Rewrite the equation $y=(2/5)x+(3/5)$ in general form: $$\begin{align*} y&=\dfrac{2}{5}x+\dfrac{3}{5}\\ 5y&=2x+3\\ 2x-5y+3&=0. \end{align*}$$ c) Graph the line using the points $\left(0,\dfrac{3}{5}\right)$ and $(1,1)$:
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