Question 382993
dividing by 3 and adding 16___ x^2 + y^2 + 4x - 4y = 16


completing the squares ___ x^2 + 4x + 4 + y^2 - 4y + 4 = 16 + 4 + 4


(x + 2)^2 + (y - 2)^2 = 24


r = sqrt(24) = 2 sqrt(6)