((x^{4} -1)-( x^{2}+x )=(x-1)(x+1)( x^{2} +1)-x(x+1)=(x

4

−1)−(x

2

+x)=(x−1)(x+1)(x

2

+1)−x(x+1)= )

(x+1)((x-1)(x^2+1)-x)=(x+1)(x^3-x^2-1)

вроде так....