Find the radius of the circle with equation x^2 - 4x + y^2 - 6y - 36 = 25
x^2 - 4x + y^2 - 6y - 36 = 25
x^2 - 4x + y^2 -6y = 25 + 36 complete the square on x, y
x^2 - 4x + 4 + y^2 - 6y + 9 = 25 + 36 + 4 + 9
25 + 36 + 4 + 9 = r^2
74 = r^2
sqrt (74 ) = r
