x^4-xy^3-x^3y-3x^2y+3xy^2+y^4=(x^4-x^3y)+(-3x^2y+3xy^2)+(y^4-xy^3)=x^3(x-y)-3xy(x-y)+y^3(y-x)=x^3-3xy-y^3=(x-y)(x^2+xy+y^2)-3xy=x^2-2xy+y^2=(x-y)^2=11995^2+1995^2×1996^2+1996^2=1995^2×1996^...