3*x + 1 ------- 2*x + 1
(3*x + 1)/(2*x + 1)
3/2 - 1/(2*(1 + 2*x))
3 1 - - ----------- 2 2*(1 + 2*x)
(1.0 + 3.0*x)/(1.0 + 2.0*x)
3 1 - - ------- 2 2 + 4*x
3/2 - 1/(2 + 4*x)