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: 43

Answer

Vertex: $(-1,2)$ Focus: $\left(1,2\right)$ Directrix: $x=-3$ See graph

Work Step by Step

We are given the parabola: $(y-2)^2=8(x+1)$ The standard equation is: $(y-k)^2=4p(x-h)$ Determine $h,k,p$: $h=-1$ $k=2$ $4p=8\Rightarrow p=2$ Determine the vertex: $(h,k)=(-1,2)$ Determine the focus: $(h+p,k)=\left(-1+2,2\right)=\left(1,2\right)$ Determine the directrix: $x=h-p$ $x=-1-2$ $x=-3$ Determine the two points defining the latus rectum: $x=1$ $(y-2)^2=4(2)(1+1)$ $(y-2)^2=16$ $y-2=\pm 4$ $y-2=-4\Rightarrow y=-2$ $y-2=4\Rightarrow y=6$ $\Rightarrow (1,-2),(1,6)$ Plot the points, draw the directrix, and graph the parabola:
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