1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7

为什么我按顺序做得出的是113/140,好多人都得这数

1/1×2=1-2分之1
1/2×3=2分之1-3分之1

所以:
原式
=(1-2分之1)+(2分之1-3分之1)+(3分之1-4分之1)+...+(6分之1-7分之1)
=1-7分之1
=7分之6

前后项可以互相抵消的。

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第1个回答  2013-09-21
1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-1/7
=6/7

你肯定算错了。

1\/1*2+1\/2*3+1\/3*4+1\/4*5+1\/5*6+1\/6*7+1\/7*8+1\/8*9+1\/9*10用简便方法...
1\/(x(x+1))=1\/x-1\/(x+1)所以,原等式就可以简化为1\/1-1\/10=0.9

1\/1*2+1\/2*3+1\/3*4+1\/4*5+1\/5*6+1\/6*7+1\/7*8
1\/1*2+1\/2*3+1\/3*4+1\/4*5+1\/5*6+1\/6*7+1\/7*8 =1-1\/2+1\/2-1\/3+1\/3-1\/4+1\/4-1\/5+1\/5-1\/6+1\/6-1\/7+1\/7-1\/8 =1-1\/8 =7\/8

1\/1×2×3+1\/2×3×4+1\/3×4×5+1\/4×5×6+1\/5×6×7=的解题技巧?_百度...
1\/((n-1)*n*(n+1))=0.5*(1\/(n-1)*n-1\/n*(n+1))=0.5*[(1\/(n-1)-1\/n)-(1\/n-1\/(n+1))]=0.5*(1\/(n-1)+1\/(n+1)-2\/n) 也就是说1乘2乘3的分之一就是1加上3分之一减去2分之2,再乘以0.5后得到结果6分之一 记住这个公式哦 高三毕业都要用的哈...

1\/1*2+1\/2*3+1\/3*4+1\/4*5+1\/5*6+1\/7*8
原式1\/1*2+1\/2*3+1\/3*4+1\/4*5+1\/5*6+1\/6*7+1\/7*8 =1-1\/2+1\/2-1\/3+1\/3-1\/4+1\/4-1\/5+1\/5-1\/6+1\/6-1\/7+1\/7-1\/8 =1-1\/8 =7\/8

1\/1*2+1\/2*3+1\/3*4+1\/4*5+1\/5*6= 要简算
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简算:1\/1*2+1\/2*3+1\/3*4+1\/4*5+1\/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)=1-1\/2+1\/2-1\/3+1\/3-1\/4+1\/4-1\/5+1\/5-1\/6 =1-1\/6 =5\/6

计算1\/1*2 + 1\/2*3 1\/3*4 +1\/4*5 +1\/5*6
解:原式=1-(1/2)+(1/2)-(1/3)+(1/3)-(1/4)+(1/4)-(1/5)+(1/5)-(1/6)=1-(1/6)=5/6 1\/(1×3) +1\/(3×5 )+1\/(5×7) +1\/(7×9) +1\/(9×11)1\/3*5=0.5×[(1\/3)-(1\/5)]1\/5*7=0.5×[(1\/5-1...

...2+1\/2×1\/3+1\/3×1\/4+1\/4×1\/5+1\/5×1\/6+1\/6×1\/7简便方法计算怎么算...
解:1\/1*2+1\/2*3+1\/3*4+……+1\/2008*2009 =1-1\/2+1\/2-1\/3+1\/3-1\/4++1\/2008-1\/2009 =1-1\/2009 =2008\/2009 祝你开心

1\/1*2+1\/2*3+1\/3*4+1\/4*5+1\/5*6+……1\/99*100
解:1\/1×2+1\/2×3+1\/3×4+1\/4×5+1\/5×6+……1\/99×100 =(1-1\/2)+(1\/2-1\/3)+...(1\/99-1\/100)=1-1\/100 =99\/100 (*^__^* *^__^* *^__^*)你好,能够帮助你是我最大的快乐!如有疑问请追问,如果您认可我的回答。请点击下面的【选为满意回答】按钮,谢谢!

1\/1*2+1\/2*3+1\/3*4+1\/4*5+1\/5*6=1\/6*7+1\/7*8+1\/8*9
2520分之15551

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