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: 10

Answer

$\frac{(x-3)^2}{9}+\frac{(y+\frac{1}{2})^2}{4}=1$, ellipse, center $C(3, -\frac{1}{2})$. foci $F(3\pm\sqrt 5, -\frac{1}{2})$, vertices $V_1(0, -\frac{1}{2})$ and $V_2(6, -\frac{1}{2})$. See graph.

Work Step by Step

Step 1. Rewrite the equation as $16(x^2-6x+9)+36(y^2+y+\frac{1}{4})=16\times9+9-9$ or $16(x-3)^2+36(y+\frac{1}{2}^2)=144$ Step 2. Divide both sides by 144 to get $\frac{(x-3)^2}{9}+\frac{(y+\frac{1}{2})^2}{4}=1$ which represents an ellipse with $a=3, b=2$. Step 3. The center can be found at $C(3, -\frac{1}{2})$. Step 4. To find the foci, use the relation $c^2=a^2-b^2$ to get $c=\sqrt {9-4}=\sqrt 5$ Step 5. The original foci are $(\pm\sqrt 5, 0)$, and the shifted foci are $F(3\pm\sqrt 5, -\frac{1}{2})$ Step 6. The original vertices are $(\pm3, 0)$, and the shifted vertices are $V(3\pm3, -\frac{1}{2})$ or $V_1(0, -\frac{1}{2})$ and $V_2(6, -\frac{1}{2})$. Step 7. See graph.
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