1/2+1/6+1/12......1/90
来源:百度知道 编辑:UC知道 时间:2024/06/17 17:44:16
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90
=1-1/2+1/2-1/3+1/3-1/4+...+1/9-1/10
=1-1/10
=9/10
1/2+1/6+1/12+......+1/90
=1/1*2+1/2*3+......+1/9*10
=(1/1-1/2)+(1/2-1/3)+......+(1/9-1/10)
中间正负抵消
=1-1/10
=9/10
原式=1*1/2+1/2*1/3+1/3*1/4+…+1/9*1/10
=1-1/2+1/2-1/3+1/3-1/4+…+1/9-1/10
=1-1/10 (正负1/2、1/3、1/4…都约掉)
=9/10
呵呵,加油!有什么不懂的再问,诚答!
1/2+1/6+1/12......1/90
=(1/1×2)+(1/2×3)+......+(1/9×10 )
=(1/1-1/2)+(1/2-1/3)+......+(1/9-1/10)
=1-1/2+1/2-1/3+...+1/9-1/10
=1-1/10
=9/10
(1/2) (1/4+1/6)=
1/2+1/4+1/6+1/8+.......+1/n=?
1/2*4+1/4*6+1/6*8+.......+1/2006*2008
1/2*4+1/4*6+1/6*8+1/48*50
|1/4-1/2|+|1/6-1/4|+|1/8-1/6|+....+|1/2006-1/2004|
|1/4-1/2|+|1/6-1/4|+|1/8-1/6|+.....+|1/2006-1/2004|
|1/4-1/2|+|1/6-1/4|+|1/8-1/6|+```+|1/2008-1/2006|
(1-1/2)*(1-1/4)*(1-1/6)*...........*(1-1/10)解法
(1/2-1)*(1/3-1)*(1/4-1)*(1/5-1)*(1/6-1)*(1/7-1)*(1/8-1)*(1/9-1)*(1/10-1)
1/2+1/3+1/4+1/5+1/6+....+1/n=?