y+2 + 8/(y-2) = ( (y+2)(y-2) + 8)/(y-2) = (y^2 - 4 + 8)/(y-2) = (y^2+4)/(y-2) (1)
(y^2+4)/(4-4y+y^2) = (y^2+4)/(y-2)^2 (2)
(1) : (2) = (y^2+4)/(y-2) * (y-2)^2/(y^2+4) = y-2
