(2x^4-4x^3y-2x^2y^2)-(x^4-2x^2y^2+y^3)+(-x^4+4x^3y-y^3)
=2x^4-4x^3y-2x^2y^2-x^4+2x^2y^2-y^3-x^4+4x^3y-y^3
=2x^4-x^4-x^4+4x^3y-4x^3y-2x^2y^2+2x^2y^2-y^3-y^3
=4x^3y-4x^3y-2x^2y^2+2x^2y^2-y^3-y^3
=-2x^2y^2+2x^2y^2-y^3-y^3
=-y^3-y^3
=-2y^3
=-2*(-1)^3
=-2*(-1)
=2
化简结果与x无关,
原式=2x^4-4x^3y-2x^2y^2-x^4-2x^2y^2-y^3-x^4+4x^3y-y^3=2×y^3
所以结果与x没关系