Calculus: Early Transcendentals 9th Edition

Published by Cengage Learning
ISBN 10: 1337613924
ISBN 13: 978-1-33761-392-7

Chapter 10 - Section 10.5 - Conic Sections - 10.5 Exercises - Page 708: 16

Answer

The foci are $(3,\pm 4\sqrt{2}-1)$ and the vertices are $(3,-7)$ and $(3,5)$.

Work Step by Step

Recall: The ellipse $\frac{(x-h)^2}{b^2}+\frac{(y-k)^2}{a^2}=1$ for $a\geq b$ has the foci at $(h,\pm c+k)$ and the vertices at $(h,\pm a+k)$. We have $9x^2-54x+y^2+2y+46=0$ $9x^2-54x+81+y^2+2y+1+46=81+1$ $9(x^2-6x+9)+(y+1)^2+46=82$ $9(x-3)^2+(y+1)^2=36$ $\frac{9(x-3)^2}{36}+\frac{(y+1)^2}{36}=1$ $\frac{(x-3)^2}{2^2}+\frac{(y-(-1))^2}{6^2}=1$ Then, $h=3$, $k=-1$, $b=2$, and $a=6$ $c=\sqrt{a^2-b^2}=\sqrt{6^2-2^2}=\sqrt{36-4}=\sqrt{32}=4\sqrt{2}$ So, the foci are $(3,\pm 4\sqrt{2}-1)$ and the vertices are $(3,-7)$ and $(3,5)$.
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