Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 11 - Section 11.1 - Parabolas - 11.1 Exercises - Page 788: 22

Answer

(a) Focus: $F(-\frac{5}{4},0)$ Directrix: $x=\frac{5}{4}$ $Focal~diameter=5$ (b)

Work Step by Step

Equation of a parabola with horizontal axis: $y^2=4px$ $x+\frac{1}{5}y^2=0$ $\frac{1}{5}y^2=-x$ $y^2=-5x$ $4p=-5$ $p=-\frac{5}{4}$ Focus: $F(p,0)=F(-\frac{5}{4},0)$ Directrix: $x=-p=\frac{5}{4}$ $Focal~diameter=|4p|=5$
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