Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 10 - Parametric Equations and Polar Coordinates - 10.5 Conic Sections - 10.5 Exercises - Page 720: 30

Answer

Ellipse Vertices are (1 +/- $\sqrt 2$, 2) Foci are (0,2), (2,2)

Work Step by Step

$x^{2}$ - 2x + $2y^{2}$ - 8y + 7 = 0 $x^{2}$ - 2x + $2y^{2}$ - 8y = -7 $x^{2}$ - 2x +1 + $2(y^{2}-4y+4)$ = -7 + 1 + 2(4) $(x-1)^{2}$ + 2$(y-2)^{2}$ = -7 + 1 + 8 = 2 $(x-1)^{2}$ + 2$(y-2)^{2}$ = 2 $\frac{(x-1)^{2}}{2}$ + $\frac{(y-2)^{2}}{1}$ = 1 This is an ellipse; the center is at (1,2) The vertices are (1 +/- $\sqrt 2$, 2) For the foci, we know from the equation of the ellipse that $a^{2}$ = 2; $b^{2}$ = 1 $c^{2}$ = $a^{2}$ - $b^{2}$ $c^{2}$ = 2-1 $c^{2}$ = 1 c = 1 The Foci are (0,2), (2,2)
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