是这样吗?
(a/(a-1)-2/(a²-1))/(1-1/(a+1))
=(a/(a-1)-2/[(a+1)(a-1)])/[(a+1-1)/(a+1)]
={[a(a+1)-2]/[(a+1)(a-1)]}/[a/(a+1)]
=(a²+a-2)/[(a+1)(a-1)]*(a+1)/a
=(a-1)(a+2)/(a-1)*a
=(a+2)/a
=1+2/a
=1+√2