十万火急!分式的加减法(1/a-1)-(2/1-a^2)
问题描述：
十万火急!分式的加减法(1/a-1)-(2/1-a^2)
“/”是分数线.十万火急!
最后答案是：(a+3)/(a^2-1),.
答
1/a-1-2/1-a^2
=1/(a-1)+2/(a+1)(a-1)
=1/(a-1)*(a+3)/(a+1)
=(a+3)/(a^2-1)