Question 43761
x^2 + y^2 - 6x + 8y + 21 = 0
(x^2 - 6x) + (y^2 + 8y) = -21
(x - 3)^2 + (y + 4)^2 = -21 + 16 + 9
(x - 3)^2 + (y + 4)^2 = 4
C(3,-4)
radius = 2 units