<PRE><B>Question 145227</B>
Find the foci of a hyperbola with the equation 9y2 - 72y - 16x2 - 64x - 64 = 0.
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9(y^2 - 8y + 16) - 16(x^2 -4x + 4) = 64+9*16-4*16

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9(y -4)^2 - 16(x - 2)^2 = 144

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[(y -4)^2/16] - [(x - 2)^2/4]  = 1
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Center at (2,4); a = 4 ; b = 2 ; therefore c = sqrt(a^2+b^2) = 2sqrt(5)
Focus at (2, 4+2sqrt(5)) and (2,4-2sqrt(5))
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Cheers,
Stan H.</PRE>