College Algebra (6th Edition)

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

Chapter 7 - Mid-Chapter Check Point - Page 688: 5

Answer

See graph Foci: $(2-4\sqrt{2},-3),(2+4\sqrt{2},-3)$

Work Step by Step

We are given the equation: $x^2+9y^2-4x+54y+49=0$ Bring the equation to the standard form:: $(x^2-4x+4)+(9y^2+54y+81)-4-81+49=0$ $(x^2-4x+4)+9(y^2+6y+9)-36=0$ $(x-2)^2+9(y+3)^2=36$ $\dfrac{(x-2)^2}{36}+\dfrac{9(y+3)^2}{36}=1$ $\dfrac{(x-2)^2}{36}+\dfrac{(y+3)^2}{4}=1$ Determine $a,b,c$ from the standard equation $\dfrac{x-h)^2}{a^2}+\dfrac{(y-k)^2}{b^2}=1$: $h=2$ $k=-3$ $a^2=36\Rightarrow a=\sqrt{36}=6$ $b^2=4\Rightarrow b=\sqrt 4=2$ $c^2=a^2-b^2$ $c^2=36-4$ $c^2=32$ $c=\pm\sqrt {32}$ $c=4\sqrt 2$ The center is: $(h,k)=(2,-3)$ The endpoints of the major and minor axis are: $(h-a,k)=(2-6,-3)=(-4,-3)$ $(h+a,k)=(2+6,-3)=(8,-3)$ $(h,k-b)=(2,-3-2)=(2,-5)$ $(h,k+b)=(2,-3+2)=(2,-1)$ The foci are: $F_1(h-c,k)=(2-4\sqrt{2},-3)$ $F_2(h+c,k)=(2+4\sqrt{2},-3)$
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