# How can I transform the circle \$x^2+y^2+a x+b y+c=0\$ into \$ (x-A)^2+(y-B)^2+C=0\$

I want Mathematica to put the circle given by $$x^2+y^2+a x+b y+c=0$$ into the standard form $$(x-A)^2+(y-B)^2+C=0$$, but I haven’t been able to.

I tried:

``````Solve(
CoefficientList(x^2 + y^2 + a x + b y + c = 0, x) ==
CoefficientList((x - A)^2 + (y - B)^2 + C = 0,
{x, y}))
``````

but it’s wrong and I don’t understand why.