20121220444 x^8-y^8=(x^4)^2-(y^4)^2=(x^4+y^4)(x^4-y^4)=(x^4+y^4)[(x²)²-(y²)²]=(x^4+y^4)(x²+y²)(x²-y²)=(x^4+y^4)(x²+y²)(x+y)(x+-y)