a-1/a²-1+a/a+1；
=（a-1）/(a+1)(a-1) + a/(a+1)
= 1/(a+1) + a/(a+1)
= （1+a）/(a+1)
=1
1/m²-m+m-3/m²-1.
=1/m(m-1) +(m-3)/(m+1)(m-1)
=(m+1+m^2 -3m)/m(m+1)(m-1)
=(m^2-2m+1)/m(m+1)(m-1)
=(m-1)^2/m(m+1)(m-1)
=(m-1)/m(m+1)
【有什么不明白可以继续追问O(∩_∩)O 】
【如果满意,请及时选为满意答案,