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