Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 1 - Section 1.4 - Linear Functions and Slope - Exercise Set - Page 213: 17


point-slope form: $y=-4(x+4)$ slope-intercept form: $y=-4x-16$

Work Step by Step

RECALL: (1) The slope-intercept form of a line's equation is: $y=mx+b$ where m = slope and b = y-intercept (2) The point-slope form of a line's equation is: $y-y_1=m(x-x_1)$ (a) point-slope form The given line has a slope of $-4$ and passes through the point $(-4, 0)$. Substitute these values into the point-slope form above to obtain: $y-0=-4[x-(-4)] \\y = -4(x+4)$ (b) slope-intercept form Substitute the slope $-4$ to $m$ to obtain the tentative equation: $y=-4x+b$ The line passes through $(-4, 0)$. This means that the coordinates of this point satisfy the equation of the line. Substitute the x and y-coordinates of this point into the tentative equation to obtain: $y=-4x+b \\0 = -4(-4) + b \\0 = 16 + b \\0-16 = b \\-16= b$ Thus, the equation of the line is $y=-4x-16$.
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