How do you find the center and radius of an equation

The center-radius form of the circle equation is in the format (x – h)2 + (y – k)2 = r2, with the center being at the point (h, k) and the radius being "r". This form of the equation is helpful, since you can easily find the center and the radius.

can someone me: the midsegment through the legs of an isosceles triangle is 4 in. find the sides of the triangle if its perimeter is 20 in. ,   and point g is the centroid of the right △abc with hypotenuse ab=18 in. find cg.