3^n/(1+e^n)的敛散性

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3^n/(1+e^n)的敛散性3^n/(1+e^n)的敛散性3^n/(1+e^n)的敛散性发散理由:3/e>1发散设un=3^n/(1+e^n)lim(n->∞)un=lim(n->∞)3^n/(1+

3^n/(1+e^n)的敛散性
3^n/(1+e^n)的敛散性

3^n/(1+e^n)的敛散性
发散
理由:3/e>1

发散
设un=3^n/(1+e^n)
lim(n->∞)un
=lim(n->∞)3^n/(1+e^n)
=lim(n->∞)1/(1/3^n+(e/3)^n)
=1/0
=∞