化简a/(a+1)-(5-a^2)/(a^2-1)+1,并选一个数代入求值

Question

化简a/(a+1) -(5-a^2)/(a^2 -1)+1,并选一个数代入求值

Answer 1

原式=(a²-a-5+a²+a²-1)/(a+1)(a-1)
=(3a²-a-6)/(a²-1)
令a=0
原式=-6/（-1）
=6