College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 7 - Section 7.3 - The Ellipse - 7.3 Assess Your Understanding - Page 525: 45

Answer

Center: $ \quad (-5,4)$ Foci: $ \quad (-5-2\sqrt{3},4), \quad (-5+2\sqrt{3},4)$ Vertices: $ \quad (-9,4), \quad (-1,4)$

Work Step by Step

Divide with 16 to obtain the standard form $\displaystyle \begin{aligned}\frac{(x+5)^{2}}{16}+\frac{4(y-4)^{2}}{16}&=1\displaystyle \\\frac{(x+5)^{2}}{16}+\frac{(y-4)^{2}}{4}&=1\displaystyle \end{aligned}$ 1. $ \quad $The form of the equation is (See table 3) Major axis horizontal (parallel to the x-axis)$\begin{array}{lll} \text{ Foci}&\text{ Vertices}&\text{ Equation}\\ {(h+c, k)}&{(h+a,k)}&{\displaystyle \frac{(x-h)^{2}}{a^{2}}+\frac{(y-k)^{2}}{b^{2}}=1}\\ {(h-c,k)}&{(h-a,k)}&{a \gt b \gt 0\text{ and }b^{2}=a^{2}-c^{2}}\\ \end{array}$ 2. $ \quad $Center = $(h,k)=(-5,4)$, 3.$ \quad a=4, b=2.$ Find $c: $ $c^{2}=a^{2}-b^{2}=16-4=12$ $c=\sqrt{12}=2\sqrt{3}\approx 3.464$ Vertices: $ \quad (h\pm a,k)=(-5\pm 4,4)$ $(-9,4), \quad (-1,4)$ Foci: $ \quad (h\pm c,k) = (-5\pm 2\sqrt{3},4)$
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