1/1*2+1/2*3..................+1/9*10
来源:百度知道 编辑:UC知道 时间:2024/06/26 01:19:14
快啊
1/1*2+1/2*3..................+1/9*10
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+....+(1/9-1/10)
=1-1/10
=9/10
1/1*2=1-1/2
1/2*3=1/2-1/3
...
1/9*10=1/9-1/10
所以:
1/1*2+1/2*3..................+1/9*10
=1-1/2+1/2-1/3+..+1/9-1/10
=1-1/10
=9/10
1/1*2=1-1/2
1/2*3=1/2-1/3
1/3*4=1/3-1/4
把这些加起来看看结果只剩下1-1/10=9/10
1/1*2+1/2*3..................+1/9*10
=1-1/2+1/2-1/3+1/3-1/4.....+1/9-1/10
=1-1/10
=9/10
1/1*2+1/2*3..................+1/9*10
=(1-1/2)+(1/2-1/3)+.....+(1/9-1/10)
=1-1/10
=9/10
原式=(1-1/2)+(1/2-1/3)+……+(1/9-1/10)
=1-1/10
=9/10
这题用的是裂项相消法
(1/2005-1)(1/2004-1)........(1/3-1)(1/2-1)
1+1/2+1/3+.....+1/n
1+1/2+1/3+...+1/100
1-1/2+1/3-.....-1/10
(1+1/2+1/3+1/4)×
(1-1/2)(1-1/3)(1-1/4)(1-1/5).....(1-1/1000)
1+1/(1+2)+1/(1+2+3)+...+1/(1+2+3+...+100)
1+1/(1+2)+1/(1+2+3)+-------+1/(1+2+3+----+100)
1+1/1+2+1/1+2+3+...+1/1+2+3...+2000
1+1/1+2+1/1+2+3.........+1/1+2+3.....100