What would be general formula of a circle in form of variables ?

[Murtuza Tipu]

General formula of a line is ax+b=0
Similarly can we have a general formula of a circle ?

 

[HomogenousCow]

The general formula for a line in a plane is y=mx+c
The general formula for a circle in the x-y plane is x^2+y^2=r^2 (where r is the radius of the circle)

 

[SteamKing]

The general formula for a line in a plane is y=mx+c
The general formula for a circle in the x-y plane is x^2+y^2=r^2 (where r is the radius of the circle)

There's an even more general equation for a circle, one whose center is not located at the origin.