College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 7 - Section 7.2 - The Parabola - 7.2 Assess Your Understanding - Page 515: 43

Answer

vertex: $\quad (-1,2) $ focus: $\quad (1,2)$ directrix: $\quad x=-3$

Work Step by Step

Comparing the form of the equation with table 2, $\quad \quad \quad (y-2)^{2}=8(x+1)\quad $has the form $\begin{array}{|c|c|c|c|} \hline {focus}&{directrix}&{equation}& ... opens\\ \hline {(h+a, k)}&{x=h-a}&{(y-k)^{2}=4a(x-h)}& right\\ \hline \end{array}$ $(y-2)^{2}=4(2)(x+1)\quad \Rightarrow\quad h=-1, k=2, a=2$ vertex: $\quad (-1,2) $ focus: $\quad (h+a, k)=(-1+2,2)=(1,2)$ directrix: $\quad x=h-a\quad \Rightarrow\quad x=-3$ To graph, find the endpoints of the latus rectum (line segment parallel to the directrix, containing the focus) by setting $x=1$ $(y-2)^{2}=8(1+1)$ $(y-2)^{2}=16$ $y-2=\pm 4$ $y=2\pm 4$ Endpoints of the latus rectum: $(1,-2), (1,6)$
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