（a-1）/（a²+2a+1）与（5）/（1-a²）通分后的结果是（a-1）/（0a²+2a+1）与（5）/（1-a²）通分后的结果是

（a-1）/（a²+2a+1）与（5）/（1-a²）通分后的结果是（a-1）/（0a²+2a+1）与（5）/（1-a²）通分后的结果是
（a-1）/（a²+2a+1）与（5）/（1-a²）通分后的结果是
（a-1）/（0a²+2a+1）与（5）/（1-a²）通分后的结果是

（a-1）/（a²+2a+1）与（5）/（1-a²）通分后的结果是（a-1）/（0a²+2a+1）与（5）/（1-a²）通分后的结果是

如图所示,

（a-1）/（a²+2a+1）=（a-1）/（a+1）²=（a-1）²/[（a-1）(a+1）²]
5/（1-a²）= -5/[（a-1）(a+1）]= -5(a+1）/[（a-1）(a+1）²]