-1 -------- 2 (x + 1)
-1/(x + 1)^2
-1/(1 + x)^2
-1 -------- 2 (1 + x)
-1 ------------ 2 1 + x + 2*x
-1/(1 + x^2 + 2*x)
-1/(1.0 + x)^2