Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 1 - Review - Exercises - Page 135: 125

Answer

$a)$ $y=\dfrac{2}{3}x-\dfrac{16}{3}$ $b)$ $2x-3y-16=0$ $c)$

Work Step by Step

The line that passes through the points $(-1,-6)$ and $(2,-4)$ $a)$ The point-slope form of the equation of a line is $y-y_{1}=m(x-x_{1})$, where $(x_{1},y_{1})$ is a point through which the line passes and $m$ is its slope. Two points through which the line passes are given. Use them to find the slope of the line: $m=\dfrac{y_{2}-y_{1}}{x_{2}-x_{1}}=\dfrac{-4+6}{2+1}=\dfrac{2}{3}$ Substitute the slope found and one of the points given into the point-slope form of the equation of a line formula and simplify: $y-(-6)=\dfrac{2}{3}[x-(-1)]$ $y+6=\dfrac{2}{3}(x+1)$ $y+6=\dfrac{2}{3}x+\dfrac{2}{3}$ Take $6$ to the right side and simplify to represent the equation in slope-intercept form: $y=\dfrac{2}{3}x+\dfrac{2}{3}-6$ $y=\dfrac{2}{3}x-\dfrac{16}{3}$ $b)$ To represent the equation in general form, begin by taking $y$ to the right side: $0=\dfrac{2}{3}x-y-\dfrac{16}{3}$ $\dfrac{2}{3}x-y-\dfrac{16}{3}=0$ Multiply the whole equation by $3$: $3\Big(\dfrac{2}{3}x-y-\dfrac{16}{3}=0\Big)$ $2x-3y-16=0$ $c)$
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