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: 52

Answer

Vertex: $(0,1)$ Focus: $\left(2,1\right)$ Directrix: $x=-2$ See graph

Work Step by Step

We are given the parabola: $y^2-2y=8x-1$ Put the equation in standard form: $y^2-2y+1=8x-1+1$ $(y-1)^2=8x$ The standard equation is: $(y-k)^2=4p(x-h)$ Determine $h,k,p$: $h=0$ $k=1$ $4p=8\Rightarrow p=2$ Determine the vertex: $(h,k)=(0,1)$ Determine the focus: $(h+p,k)=\left(0+2,1\right)=\left(2,1\right)$ Determine the directrix: $x=h-p$ $x=0-2$ $x=-2$ Determine the two points defining the latus rectum: $x=2$ $(y-1)^2=4(2)(2)$ $(y-1)^2=16$ $y-1=\pm 4$ $y-1=-4\Rightarrow y_1=-3$ $y-1=4\Rightarrow y_2=5$ $\Rightarrow (2,-3),(2,5)$ Plot the points, draw the directrix, and graph the parabola:
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