Question 751914
x^2 + (y - 3)^2 = 144
Multiply out the bracket.
x^2 +(y^2 - 6y + 9) = 144
x^2 + y^2 - 6y + 9 - 144 = 0
x^2 + y^2 -6y - 135 = 0

Centre (0, 3)  radius =sqrrt 0^2 + 3^2 + 135
                      = sqrrt 144
                      = 12

Hope this helps.
:-)