(n²-1)/(an²+2)的极限=3,求a

(n²-1)/(an²+2)的极限=3,求a

若n->无穷
则
上下同除n^2
=(1-1/n^2)/(a+2/n^2)
分子分母分别取极限
=（1-0）/(a+0)=3
a=1/3