4 2 x - x
x^4 - x^2
1*(x + 1)*(x + 0)*(x - 1)
((1*(x + 1))*(x + 0))*(x - 1)
2 / 2\ x *\-1 + x /
x^2*(-1 + x^2)
2 x *(1 + x)*(-1 + x)
x^2*(1 + x)*(-1 + x)