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: 33

Answer

$(y+2)^2=4(x+1)$ Latus rectum points: $(0,-4),(0,0)$ See graph

Work Step by Step

We are given the parabola: Focus: $(0,-2)$ Vertex: $(-1,-2)$ Because the vertex and the focus have the same $y$-coordinate, the parabola is horizontal. Its standard equation is: $(y-k)^2=4p(x-h)$ Use the coordinates of the vertex to determine $h,k$: $(h,k)=(-1,-2)$ $h=-1$ $k=-2$ Determine $p$ using the coordinates of the focus: $(h+p,k)=(0,-2)$ $(-1+p,-2)=(0,-2)$ $-1+p=0$ $p=1$ Determine the parabola's equation: $(y+2)^2=4(1)(x+1)$ $(y+2)^2=4(x+1)$ Determine the two points defining the latus rectum: $x=0$ $(y+2)^2=4(0+1)$ $(y+2)^2=4$ $y+2=\pm 2$ $y+2=-2\Rightarrow y_1=-4$ $y+2=2\Rightarrow y_2=0$ $\Rightarrow (0,-4),(0,0)$ Plot the points and graph the parabola:
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