2 16 - x ------------- 2 x + 8*x + 16
(16.0 - x^2)/(16.0 + x^2 + 8.0*x)
2 16 - x -------------- 16 + x*(8 + x)
4 - x ----- 4 + x
-(-4 + x) ---------- 4 + x
8 -1 + ----- 4 + x