# Equation of a circle

The general form for the equation of a circle is $$ax^2+by^2+cx+dy+e = 0$$, and the circle-radius form of the circle equation is $$(x-h)^2+(y-k)^2 = r^2$$ , with the center being at the point $$(h, k)$$ and the radius being “$$r$$”.

Think about the following question. The endpoints of the diameter of a circle are $$(-4, 0)$$ and $$(4, 0)$$. What are the coordinates of the center of this circle?