1/(12×13)+1/(13×14)+……+1/(19×20)的值为多少?是如何计算的?
来源:百度知道 编辑:UC知道 时间:2024/06/08 07:46:33
可我看见的书上答案是1/40?
答案是1/30
有个公式:1/[n(n+1)]=(n+1-n)/[n(n+1)]=1/n-1/(n+1)
这样分解后,中间的部分可以前后消去
所以原式=1/12-1/13+1/13-1/14+……-1/19+1/19-1/20
=1/12-1/20
=1/30
1/(12×13)+1/(13×14)+……+1/(19×20)
=1/12-1/13+1/13-1/14+...+1/19-1/20
=1/12-1/20
=(5-3)/60
=1/30.
1/(12×13)+1/(13×14)+1/(14×15)。。。+1/(19×20)=?
1/(12×13)+1/(13×14)+……+1/(19×20)=???
已知1-1/2=1/2 1/2-1/3=1/6 1/3-1/4=1/12 那么1/6-1/7=()1/12-1/13=()1/2+1/6+1/12=()
公务员题1/(12*13)+1/(13*14)+1/(14*15)+.......+1/(19*20)
1/11+1/12+1/13+1/14+1/15=?
.表达式DateDiff(“y”,#12/30/1999#,#1/13/2000#)的结果是
1/(12×13)+1/(13×14)+……+1/(19×20)的值为多少?是如何计算的?
1/12*13+1/13*14+.......+1/19*20
1/8=1/( )+1/( )1 1/10=1/( )+1/( )1/12=1/( )+1/( )+1/( )
比较大小:1/11+1/29 1/12+1/25 1/13+1/21 1/14+1/19