Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 11: Parametric Equations and Polar Coordinates - Section 11.6 - Conic Sections - Exercises 11.6 - Page 678: 39

Answer

$ a.\qquad$ New vertex:$\quad V'(1,-2)$ New focus: $ \quad F'(3,-2)$ New directrix: $ \quad x=-1$ $ b.\qquad$ See graph.

Work Step by Step

$ a.\qquad$ $y^{2}=8x=4(2)x$ has the form $y^{2}=4px $ ,$\qquad x=\displaystyle \frac{y^{2}}{4p}$ ,$\qquad$... opens right Vertex = $(0,0)$ Focus = $(p,0)=(2,0)$ Directrix: $x=-p=-2$ New vertex: $\left\{\begin{array}{ll} x'=x+1=0+1=1 & \text{...shift right}\\ y'=y-2=0-2=-2 & \text{...shift down} \end{array}\right., \quad V'(1,-2)$ New focus: $\left\{\begin{array}{ll} x'=x+1=2+1=3 & \text{...shift right}\\ y'=y-2=0-2=-2 & \text{...shift down} \end{array}\right., \quad F'(3,-2)$ New directrix (vertical line, shifted to the right): $x=-1$ $ b.\qquad$ See graph The vertex and focus are now on the line $y=-2$ (the x-axis is shifted down).
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