standard form of a circle = (x-a)^2 + (y-b)^2 = r^2 where (a,b) is the center and r is the radius
now, we have to account to complete the squares. since r = 7, r^2 = 49.
(x+4)^2 = x^2 + 8x + 16
(y+2)^2 + y^2 + 4y + 4
x^2 + 8x + 16 + y^2 + 4y + 4 + 49 = 0
this makes up a circle if you break it down into standard form... now lets add up what we have added onto it
49 + 4 + 16 = 49 + 20 = 69