Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 10 - Analytic Geometry - 10.2 The Parabola - 10.2 Assess Your Understanding - Page 647: 44

Answer

Vertex: $(-4,-2)$ Focus: $(-4,2)$ Directrix: $y=-6$ See graph

Work Step by Step

We are given the parabola: $(x+4)^2=16(y+2)$ The standard equation is: $(x-h)^2=4p(y-k)$ Determine $h,k,p$: $h=-4$ $k=-2$ $4p=16\Rightarrow p=4$ Determine the vertex: $(h,k)=(-4,-2)$ Determine the focus: $(h,k+p)=(-4,-2+4)=(-4,2)$ Determine the directrix: $y=k-p$ $y=-2-4$ $y=-6$ Determine the two points defining the latus rectum: $y=2$ $(x+4)^2=16(2+2)$ $(x+4)^2=64$ $x+4=\pm 8$ $x+4=-8\Rightarrow x_1=-12$ $x+4=8\Rightarrow x_2=4$ $\Rightarrow (-12,2),(4,2)$ Plot the points, draw the directrix, and graph the parabola:
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