SOLUTION: How do I identify this equation as a circle and to specify the center and the radius? {{{ x^2+y^2-8x+4y+20=0 }}} I worked on the equation and made it into the (x-h)^2+(y-k)^2

Question 116023: How do I identify this equation as a circle and to specify the center and the radius?

I worked on the equation and made it into the (x-h)^2+(y-k)^2=r form:

but I don't understand how the radius can be zero.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
x^2+y^2-8x+4y+20=0
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x^2-8x+16 + y^2+4y+4 = -20 + 16 +4
(x-4)^2 + (x+2)^2 = 0
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This is not a circle as you said.
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Cheers,
Stan H.
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