/ 2 \ 2*x 2*x*\x + 1/ ------ - ------------ 2 2 x - 1 / 2 \ \x - 1/
2.0*x/(-1.0 + x^2) - 2.0*x*(1.0 + x^2)/(-1.0 + x^2)^2
2 / 2\ / 2\ / 2\ 2*x*\-1 + x / - 2*x*\1 + x /*\-1 + x / --------------------------------------- 3 / 2\ \-1 + x /
-4*x ---------- 2 / 2\ \-1 + x /
-4*x ------------------ 2 2 (1 + x) *(-1 + x)