1/2+1/6+1/12+1/20+1/30=
来源:百度知道 编辑:UC知道 时间:2024/05/28 17:11:29
1/2+1/6+1/12+1/20+1/30
=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)-(1/5-1/6)【用乘法分配率】
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6
=1-1/6(因为加一个数再减去相同的数等于不加不减)
=5/6
=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6
=5/6
这是规律题啊!中间的一加一减等于零!最后题就是 一减六分之一,等于六分之五
1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6=5/6
用裂项法1/2+1/6+1/12+1/20+1/30=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6=5/6
5/6
1/2+1/6+1/12+1/20+1/30=15/30+5/30+1/30+1/12+1/20=21/30+1/12+1/20=14/20+1/20+1/12=....=5/6
(1/2) (1/4+1/6)=
1/2 ,1/3 ,1/6 /1/6 ,()
1/2+1/6+1/12+1/20+1/30
1/2+1/4+1/6+1/8+.......+1/n=?
-1/2-1/6-1/12-1/20-``````````````-1/4026042
1/2+1/6+1/12+......+1/1980+1/2070=?
1/2 1/6 1/3 2 ( ) 3 1/2 数字推理
1/2*4+1/4*6+1/6*8+.......+1/2006*2008
1/2*4+1/4*6+1/6*8+1/48*50
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90=