x是方程x²+3x+1=0的根,
∴x(x+3)=-1,
∴（x-3）/（3x²-6x）÷[(x+2-5(/x-2)]
=(x-3)/[3x(x-2)]÷[（x^-4-5)/(x-2)]
=(x-3)/[3x(x-2)]×(x-2)/[(x+3)(x-3)]
=1/[3x(x+3)]
=-1/3.别客气！