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

Algebra ->  Quadratic-relations-and-conic-sections -> 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      Log On


   

Question 116023: How do I identify this equation as a circle and to specify the center and the radius?
+x%5E2%2By%5E2-8x%2B4y%2B20=0+
I worked on the equation and made it into the (x-h)^2+(y-k)^2=r form:
+%28x-4%29%5E2%2B%28y%2B2%29%5E2=0+
but I don't understand how the radius can be zero.
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
x^2+y^2-8x+4y+20=0
--------
x^2-8x+16 + y^2+4y+4 = -20 + 16 +4
(x-4)^2 + (x+2)^2 = 0
-----------------------
This is not a circle as you said.
-----------------------
Cheers,
Stan H.