结果是max{a_i},i=1,2,....k
夹逼准则,假设a_p=max{a_i},i=1,2,....k
[(a_p)^n]^(1/n)=<[(a_1)^n+(a_2)^n+(a_3)^n+....(a_k)^n]^(1/n)<=[n(a_p)^n]^(1/n)
即(a_p)=<[(a_1)^n+(a_2)^n+(a_3)^n+....(a_k)^n]^(1/n)<=(a_p)*n^(1/n)
因为n->无穷
lim a_p=a_p
lim(a_p)*n^(1/n)=a_p
夹逼可得原式的极限为a_p。即为ai中的最大者。