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