Chứng minh lim: $\lim_{x->+\infty }\frac{2^{n-1}}{(n+1)!}$ =0
Edited by reyesmovie, 14-11-2014 - 16:39.
Chứng minh lim: $\lim_{x->+\infty }\frac{2^{n-1}}{(n+1)!}$ =0
Edited by reyesmovie, 14-11-2014 - 16:39.
Đặt $a_n= \frac{2^{n-1}}{(n+1)!}$. Ta thấy $\sum a_n$ hội tụ là vì
$$\frac{a_{n+1}}{a_n}=\frac{2^n}{(n+2)!}\frac{(n+1)!}{2^{n-1}}=\frac{2}{n+2} \rightarrow 0 <1$$
Vì $\sum a_n$ hội tụ, nên $a_n \rightarrow 0$.
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