# alg. 2

what is the foci of the ellipse

X2 over 81 + Y2 over 49=1

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1. the ellipse would be horizontal (since a > b), so the foci would be (h +/- c, k). h is 0 and k is also 0. a is 9 and b is 7. a^2 = b^2 + c^2
81 = 49 + c^2
32 = c^2
4 x the square root of 2 = c

so the foci would be (+/- the square root of 2, 0)

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