Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 10 - Analytic Geometry - 10.2 Ellipses - 10.2 Exercises - Page 979: 21

Answer

$\dfrac{x^2}{5}+\dfrac{y^2}{9}=1$

Work Step by Step

The standard form of an ellipse can be written as: $\dfrac{x^2}{b^2}+\dfrac{y^2}{a^2}=1....(1); $ when $b \gt a$ has foci $(0, \pm c)$ where ; $c^2=a^2-b^2$ We are given that an ellipse with major axis is $6$ . So, $2a=6 \implies a=3$ and $a^2 =9$.and $x$-intercept at $\pm {15}$ and $y$-intercept at $\pm 4$ due to the intercepts, the centre will be at origin. Foci are: $(0,-2)$ and $(0,2)$; This implies that $c=2$ Therefore, $c^2=a^2-b^2 \implies 2^2 =3^2-b^2 \implies b^2= 5$ Now, substitute these values into the equation (1) to obtain: $\dfrac{x^2}{5}+\dfrac{y^2}{9}=1$
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