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