**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?