Write the euation of a circle with center at (0,-9) and radius 15

Question

I need to find the equation of a circle. Write the euation of a circle with center at (0,-9) and radius 15

Answer 1

Circle equation is (x-h)^2+(y-k)^2 = r^2

Given (h,k) = (0,-9) and r = 15

(x-0)^2+(y+9)^2 = 15^2

x^2+y^2+81+18y = 225

Subtract 225 from each side.

Required circle equation is x^2+y^2+18y-144 = 0.