2 x - 7*x --------------- 2 7*x + 13*x - 2
(x - 7.0*x^2)/(-2.0 + 7.0*x^2 + 13.0*x)
x*(1 - 7*x) ----------------- -2 + x*(13 + 7*x)
-x ----- 2 + x
2 -1 + ----- 2 + x