通分:(1)1/a+1,3/1-a,5/a^2-1 (2)a/a^2-4,a-1/a-2,a+2/a^2-4a+4
问题描述：
通分:(1)1/a+1,3/1-a,5/a^2-1 (2)a/a^2-4,a-1/a-2,a+2/a^2-4a+4
答
(1)1/a+1=(a-1)/(a+1)(a-1)
3/1-a=-3(a+1)/(a+1)(a-1)
5/a^2-1 =5/(a+1)(a-1)
(2)a/a^2-4=a(a-2)/(a+2)(a-2)²
a-1/a-2=(a-1)(a+2)(a-2)/(a+2)(a-2)²
a+2/a^2-4a+4=(a+2)²/(a+2)(a-2)²