The center of the circle x^2 + y^2 = 8x - 16y - 34 with equation is the point (x,y). What is x + y?
+36916 x^2 - 8x + y^2 + 16y = - 34 'complete the square ' for x and y
(x-4)2 (y+8)2 = -34 + 16 + 64
this is circle in form (x-h)^2 + (y-k)^2 = r^2 form center is h, k take it from here ! 
