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