2 4*x + 2*x - 6 -------------- 2 x - 1
(-6.0 + 2.0*x + 4.0*x^2)/(-1.0 + x^2)
2*(-3 + x*(1 + 2*x)) -------------------- 2 -1 + x
2*(3 + 2*x) ----------- 1 + x
2 4 + ----- 1 + x