2 2*x + x - 1
2*x^2 + x - 1
2 -1 + x + 2*x
-1 + x + 2*x^2
(x + 1)*(x - 1/2)
(1 + x)*(-1 + 2*x)
-1 + x*(1 + 2*x)
-1.0 + x + 2.0*x^2