Question 392026
 The graph of the function x^2+y^2+20x-16y+80=0 is a circle. What are the coordinates of the center and the length of the radius?

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Complete the square:
x^2+20x+100 + y^2-16y+64 = -80+100+64
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Factor:
(x+10)^2 + (y-8)^2 = 84
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Center: (-10,8)
Radius: sqrt(84) = 2sqrt(21)
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Cheers,
Stan H.