Question

a＞0,b＞0,求当n趋于无穷大时（a＾1／n＋b＾1／n）＾n／2＾n的极限

Answer 1

原式=lim{n->∞}{[1+(a^{1/n}+b^{1/n}-2)/2]^{1/(a^{1/n}+b^{1/n}-2)}}^{n/(a^{1/n}+b^{1/n}-2)}

=e^(lim{n->∞}{(a^{1/n}+b^{1/n}-2)/{1/n}})=e^(lim{n->∞}{(a^{1/n}-1)/{1/n}+(b^{1/n}-1)/{1/n}})

=e^{lna+lnb}=e^{lnab}=a