Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 10 - Parametric Equations and Polar Coordinates - 10.5 Conic Sections - 10.5 Exercises - Page 720: 9

Answer

The equation of a parabola becomes: $y^{2}=-x$ which has focus $(-\frac{1}{4},0)$ and directrix is $x=\frac{1}{4}$.

Work Step by Step

The equation of a parabola with vertex $(0,0)$ is $y^{2}=4px$.It has focus $(p,0)$ and directrix $x=-p$. Take $(-1,1)$ a point shown on the curve. Thus, $(1)^{2}=4p(-1)$ or, $p=-\frac{1}{4}$ Hence, the equation of a parabola becomes: $y^{2}=-x$ which has focus $(-\frac{1}{4},0)$ and directrix is $x=\frac{1}{4}$.
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