Разложить на множители x^8+x^4-2
x^8+x^4-2=
(x^4+1/2)^2-(3/2)^2=
(x^4+1/2+3/2)(x^4+1/2-3/2)=
(x^4+2)(x^4-1)=
(x^4+2)(x^2+1)(x^2-1)=
(x^4+2)(x^2+1)(x-1)(x+1)