=(x^6-x^4)-(x²-1)=x^4(x²-1)-(x²-1)=(x²-1)(x^4-1)=(x-1)(x+1)(x²-1)(x²+1)=
(x-1)(x+1)(x-1)(x+1)(x²+1)=(x-1)²(x+1)²(x²+1)
