(x^2-2x-3/x^2-1-x+1/x-1)÷x-3/x-1=[(x-3)(x+1)/(x-1)(x+1)-(x+1)/(x-1)]×(x-1)/(x-3)=[(x-3)/(x-1)-(x+1)/(x-1)×(x-1)/(x-3)=-4/(x-1)×(x-1)/(x-3)=-4/(x-3)当x=2时原式=-4/(2-3)=4
