x/(x平方-x-2)除以x/(x+1)减x+2/x平方-4
=x/(x+1)(x-2)*(x+1)/x-(x+2)/(x+2)(x-2)
=1/(x-2)-1/(x-2)
=0对不起，是2x/(x平方-x-2)除以x/(x+1)减x+2/x平方-42x/(xƽ��-x-2)����x/(x+1)��x+2/xƽ��-4=2x/(x+1)(x-2)*(x+1)/x-(x+2)/(x+2)(x-2)=2/(x-2)-1/(x-2)=1/(x-2)