We have the following equation:
x2 + y2 + 6y - 72 = 0
Rewriting we have:
x2 + y2 + 6y = 72
Complete squares we have:
x2 + y2 + 6y + (6/2) ^ 2 = 72 + (6/2) ^ 2
x2 + y2 + 6y + (3) ^ 2 = 72 + (3) ^ 2
x2 + y2 + 6y + 9 = 72 + 9
x2 + (y + 3) 2 = 81
So, the center is:
(0, -3)
The radio is:
r = 9
Answer:
(0, -3)
r = 9