3 a + a ------ 4 a + a
(a^3 + a)/(a^4 + a)
2/(3*(1 + a)) + (1 + a)/(3*(1 + a^2 - a))
2 1 + a --------- + -------------- 3*(1 + a) / 2 \ 3*\1 + a - a/
2 1 + a ------ 3 1 + a
(1 + a^2)/(1 + a^3)
2 1 + a -------------------- / 2 \ (1 + a)*\1 + a - a/
(1 + a^2)/((1 + a)*(1 + a^2 - a))
(a + a^3)/(a + a^4)