(x-3xy-y)分之(2x+3xy-2y) 分子分母同时除以xy得
=(1/y-3-1/x)分之(2/y+3-2/x)
=[-(1/x-1/y)-1]分之(-2(1/x-1/y)+3)
=(-3-1)分之(-6+3)
=(-4)分之(-3)
=4分之3