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: 46

Answer

Center: $\quad \quad (3,-2)$ Foci: $\quad \quad (3,2), \quad (3,-6)$ Vertices: $\quad (3,-2+3\sqrt{2}), \quad (3,-2-3\sqrt{2})$

Work Step by Step

Divide with $18$ to obtain the standard form $\displaystyle \begin{aligned}\frac{9(x-3)^{2}}{18}+\frac{(y+2)^{2}}{18}&=1\displaystyle \\\frac{(x-3)^{2}}{2}+\frac{(y+2)^{2}}{18}&=1\displaystyle \end{aligned}$ 1. $ \quad $The form of the equation is (See table 3) Major axis vertical (parallel to the y-axis) $\begin{array}{lll} \text{ Foci}&\text{ Vertices}&\text{ Equation}\\ {(h,k+c)}&{(h,k+a)}&{\displaystyle \frac{(x-h)^{2}}{b^{2}}+\frac{(y-k)^{2}}{a^{2}}=1}\\ {(h,k-c)}&{(h,k-a)}&{a \gt b \gt 0\text{ and }b^{2}=a^{2}-c^{2}}\end{array}$ 2. $ \quad $Center = $(h,k)=(3,-2)$, 3.$ \quad a=\sqrt{18}=3\sqrt{2},\quad \quad b=\sqrt{2}$ $(a\approx 4.243 \quad \quad b\approx 1.414 )$ Find $c: $ $c^{2}=a^{2}-b^{2}=18-2=16$ $c=4$ Vertices: $ \quad (h,k\pm a)=(3,-2\pm 3\sqrt{2})$ Foci: $ \quad (h,k\pm c) = (2,3\pm 4)$ $(3,2), \quad (3,-6)$
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