College Algebra (6th Edition)

Published by Pearson
ISBN 10: 0-32178-228-3
ISBN 13: 978-0-32178-228-1

Chapter 7 - Conic Sections - Exercise Set 7.1 - Page 672: 73

Answer

Different centres (the endpoints, the foci are translated accordingly)

Work Step by Step

We are given the two ellipses: $\dfrac{x^2}{25}+\dfrac{y^2}{16}=1$ $\dfrac{(x-1)^2}{25}+\dfrac{(y-1)^2}{16}=1$ The standard equation for each ellipse is: $\dfrac{(x-h)^2}{a^2}+\dfrac{(y-k)^2}{b^2}=1$ Determine $h,k,a,b,c$ for the ellipse $\dfrac{x^2}{25}+\dfrac{y^2}{16}=1$: $h=0$ $k=0$ $a^2=25\Rightarrow a=\sqrt{25}=5$ $b^2=16\Rightarrow b=\sqrt{16}=4$ $c^2=a^2-b^2$ $c^2=25-16$ $c^2=9$ $c=\sqrt 9=3$ The centre of the ellipse is $C_1(0,0)$, the length of the major axis is $2a=2(5)=10$, the length of the minor axis is $2b=2(4)=8$. Determine $h,k,a,b,c$ for the ellipse $\dfrac{(x-1)^2}{25}+\dfrac{(y-1)^2}{16}=1$: $h=1$ $k=1$ $a^2=25\Rightarrow a=\sqrt{25}=5$ $b^2=16\Rightarrow b=\sqrt{16}=4$ $c^2=a^2-b^2$ $c^2=25-16$ $c^2=9$ $c=\sqrt 9=3$ The centre of the ellipse is $C_2(1,1)$, the length of the major axis is $2a=2(5)=10$, the length of the minor axis is $2b=2(4)=8$. The two ellipses have different centres (the endpoints, the foci are translated accordingly).
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