1/a+1-a+3/a^2-1xa^2-2a+1/a^2+4a+3你这式子真像天书哦!!楼主的意思应该是:1/(a+1) -[(a+3)/(a^2-1)]*[(a^2-2a+1)/(a^2+4a+3)]解:原式=1/(a+1) -{(a+3)/[(a-1)(a+1)]}*{(a-1)^2/[(a+3)(a+1)]} =1/(a+1) -(a-1)/(a+1)^2 =2/(a+1)^2