Calculus: Early Transcendentals 9th Edition

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

Chapter 10 - Review - Exercises - Page 721: 52

Answer

Foci: $(-1,\pm\sqrt{21}+2)$ Vertices: $(-1,7)$ and $(-1,-3)$

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 $25x^2+4y^2+50x-16y=59$. Rewrite the equation above: $25x^2+50x+25+4y^2-16y+16=59+25+16$ $25(x+1)^2+4(y-2)^2=100$ $\frac{(x+1)^2}{4}+\frac{(y-2)^2}{25}=1$ Then, $h=-1,k=2,b=2$ and $a=5$ $c=\sqrt{a^2-b^2}=\sqrt{5^2-2^2}=\sqrt{25-4}=\sqrt{21}$ So, the foci are $(-1,\pm \sqrt{21}+2)$ and the vertices are $(-1,7)$ and $(-1,-3)$. Sketch the graph:
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