Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 11 - Section 11.4 - Shifted Conics - 11.4 Exercises - Page 815: 47

Answer

$(y-4)^2=4(x+4)$ Parabola: vertex $V(-4, 4)$, focus $F(-3,4)$, directrix $x=-5$ See graph.

Work Step by Step

Step 1. Make squares of the variable: $y^2-8y=4x$, $(y-4)^2=4x+16$, or $(y-4)^2=4(x+4)$ Step 2. We can identify the conic as a parabola with a vertex at $V(-4, 4)$ Step 3. From the equation in step-1, we have $4p=4$ and $p=1$ Step 4. Use shifts from the center, we can identify the focus at $F(-3,4)$, and the directrix as $x=-5$ Step 5. Graph the function as shown.
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