(1)已知x+y=6, xy=-3x^2y+xy^2=xy(x+y)=-3*6=-18(2)x*[2-(1/x)]+(x/x^2-2x)*(x^2-4)=x*(2x-1)/x+[x/x(x-2)]*(x+2)(x-2)=(2x-1)+(x+2)(x-2)/(x-2)=2x-1+x+2=3x+1