Question

Find the equation of the circle in the form of
x^2+y^2+Dx+Ey+F=0, using the three points.

(-3,-1),(2,4),(-6,8)

The answer should be x^2+y^2+6x-8y=0
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(-3)^2+(-1)^2-3d-e+f=0
(2)^2+(4)^2+2d+4e+f=0
(-6)^2+(8)^2-6d+8e+f=0
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10-3d-e+f=0
20+2d+4e+f=0
100-6d+8e+f=0
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-3d-e+f=-10
2d+4e+f=-20
-6d+8e+f=-100
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