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: 47

Answer

Vertex: $(2,-3)$ Focus: $\left(4,-3\right)$ Directrix: $x=0$ See graph

Work Step by Step

We are given the parabola: $(y+3)^2=8(x-2)$ The standard equation is: $(y-k)^2=4p(x-h)$ Determine $h,k,p$: $h=2$ $k=-3$ $4p=8\Rightarrow p=2$ Determine the vertex: $(h,k)=(2,-3)$ Determine the focus: $(h+p,k)=\left(2+2,-3\right)=\left(4,-3\right)$ Determine the directrix: $x=h-p$ $x=2-2$ $x=0$ Determine the two points defining the latus rectum: $x=4$ $(y+3)^2=4(2)(4-2)$ $(y+3)^2=16$ $y+3=\pm 4$ $y+3=-4\Rightarrow y_1=-7$ $y+3=4\Rightarrow y_2=1$ $\Rightarrow (4,-7),(4,1)$ Plot the points, draw the directrix, and graph the parabola:
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