试证明(x^3+3x^2y-2xy^2+1)+(x^3-4x^2y+3xy^2-10)+(-xy^2+x^2y-2x^3+3)的值与x,y无关

(x^3+3x^2y-2xy^2+1)+(x^3-4x^2y+3xy^2-10)+(-xy^2+x^2y-2x^3+3)=x^3+3x^2y-2xy^2+1+x^3-4x^2y+3xy^2-10-xy^2+x^2y-2x^3+3=x^3+x^3-2x^3+3x^2y+x^2y-4x^2y+3xy^2-2xy^2-xy^2+3+1-10=3+1-10=-6所以(x^3+3x^2y-2xy^2+1...