Calculus: Early Transcendentals 9th Edition

Published by Cengage Learning
ISBN 10: 1337613924
ISBN 13: 978-1-33761-392-7

Chapter 10 - Section 10.5 - Conic Sections - 10.5 Exercises - Page 709: 28

Answer

Type: Parabola Vertex $(0,-3)$ Focus: $\left(0,-2\frac{15}{16}\right)$

Work Step by Step

Rewrite the equation: $4x^2=y+4$ $y+4=4x^2$ $\frac{1}{4}(y+4)=x^2$ $\frac{1}{4}(y-(-3))=(x-0)^2$ Recall: The equation $4p(y-b)=(x-a)^2$ describes a vertical parabola whose vertex is $(a,b)$ and the focus is $(a,p+b)$. We have $a=0$ and $b=-3$ $4p=\frac{1}{4}\to p=\frac{1}{16}$ $p+b=\frac{1}{16}+(-3)=-2\frac{15}{16}$ Then, the given equation describes a vertical parabola whose vertex is $(0,-3)$ and the focus is $\left(0,-2\frac{15}{16}\right)$.
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