Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 11 - Review - Test - Page 835: 12

Answer

$(y+4)^2=-2(x-4)$, parabola, vertex $V(4, -4)$, focus $F(\frac{7}{2}, -4)$, directrix $x=\frac{9}{2}$ See graph.

Work Step by Step

Step 1. Rewrite the equation as $y^2+8y+16=-2x-8+16$ or $(y+4)^2=-2(x-4)$ which represents a parabola. Step 2. The vertex can be found at $V(4, -4)$. Step 3. To find the focus, compare the equation with a standard form to get $4p=-2$ and $p=-\frac{1}{2}$ and thus the focus is at $F(4-\frac{1}{2}, -4)$ or $F(\frac{7}{2}, -4)$ Step 4. The original directrix is $x=\frac{1}{2}$ and the shifted directrix is $x=4+\frac{1}{2}=\frac{9}{2}$ Step 5. See graph.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.