Question

(x-y)(x+y)(x2+y2)(x4-y4)-x8=-y8

Answer 1

$(x-y)(x+y)(x^2+y^2)(x^4-y^4)-x^8 = \ (x^2-y^2)(x^2+y^2)(x^4-y^4)-x^8 = \ (x^4-y^4)(x^4-y^4)-x^8=(x^4-y^4)^2-x^8=y^8-2x^4y^4$ 
 возможно там +