什么狗聪明,最听话:排列求和 3/（1！+2！+3！）+4/（2！+3！+4！）+（N+2）/[N！+（N+1）！+（N+2）！] 很紧急！

来源：百度文库 编辑：高考问答 时间：2024/05/03 06:22:52
今晚谁能解答啊？很着急！

我刚学哈~~~
3/（1！+2！+3！)=3/(1+2*1+3*2*1)=1/3 ①
4/（2！+3！+4！)=4/(2*1+3*2*1+4*3*2*1)=1/8 ②
(N+2）/[N！+（N+1）！+（N+2）！] =(N+2)/[N!+(N+1)*N!+(N+2)*(N+1)*N!]
=(N+2)/[N!+(N+1)*N!+(N2+3N+2)*N!]
N2 为N的平方哦~~ =(N+2)/[(1+N+1+N2+3N+2)*N!]
=(N+2)/[(N2+4N+4)*N!]
(N+2)2 为N+2的平方哦~~ =(N+2)/(N+2)2*N!
=1/(N+2)N! ③
①+②+ ③=11/24+1/(N+2)*N!

算详细了把~~~呼~~

哎

排列求和 3/（1！+2！+3！）+4/（2！+3！+4！）+（N+2）/[N！+（N+1）！+（N+2）！] 很紧急！ 排列求和 3/（1！+2！+3！）+4/（2！+3！+4！）+...+（N+2）/[N！+（N+1）！+（N+2）！] 1×2+3×4+5×8 求和 求和1*2+2*3+...+(n-1)n 求和:1+1/2^2+1/3^2+...+1/n^2 求和：1+1/2+1/3+1/4+…+1/n=? 求和：S=1+1/2+1/3+1/4+。。。+1/n 求和:1+1/2+1/3+¼+…+1/n=? 求和：S=1+1/2+1/3+。。。+1/10 求和: 1/2+2/4+3/8+......+n/2^n