1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72

简便计算1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72
1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72 =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 裂项相加

1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72+1\/90怎么简便计算?
1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72+1\/90=9\/10 方法：裂项相消法 1\/[n(n+1)]=（1\/n）- [1\/(n+1)]由题意得：1\/6=1\/[2（2+1）]、1\/12=1\/[3（3+1）]、1\/20=1\/[4（4+1）]、1\/30=1\/[5（5+1）]、依次可以表达为1\/[n(n+1)]的形式。所以可得：...

1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72= 简便计算,快!
1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72 =1\/(1*2)+1\/(2*3)+1\/(3*4)+...+1\/(8*9)=1-1\/2+1\/2-1\/3+...+1\/8-1\/9 =1-1\/9 =8\/9

数学:计算 1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72+1\/90=? (例:1\/2...
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\/8-1\/9)+(1\/9-1\/10)=1-1\/10 =9\/10

...的数学题:1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72求简便方法_百度知 ...
1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72 把1\/6项以后的各项都拆成两项，形成前后可以+-抵消的项，使计算简便 =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\/8-1\/9）=1\/2+1\/2-1\/9 =1-1\/9 =8\/9 ...

1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56 +1\/72+1\/90=?【简便方法】_百度知 ...
原式=1\/(1*2)+1\/(2*3)+...+1\/(9*10)1\/(n*(n+1))=1\/n-1(n+1)所以 原式=1\/1-1\/2+1\/2-1\/3+1\/3-1\/4+...+1\/8-1\/9+1\/9-1\/10=1\/1-1\/10=9\/10

1\/2十1\/6十1\/12十1\/20十1\/30十1\/42十1\/56十1\/72.怎样做
1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72=8\/9 这样算是因为他有8个数,分子就是8,然后再用最后一个分数的分母除8就是分子

1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72怎么简便计算?
1\/2+1\/6+1\/12+1\/20＋1\/30+1\/42+1\/56+1\/72 =1-1\/2+1\/2-1\/3+1\/3-1\/4+...+1\/7-1\/8+1\/8-1\/9 =1-1\/9 =8\/9 =9分之8 朋友，请【采纳答案】，您的采纳是我答题的动力，谢谢。

1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72=?
1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72 =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\/8-1\/9 =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\/8）-1\/9 =1+0-1\/9 =1-1\/9 =8\/9 =9分...

...的数学题:1\/2+1\/6+1\/12+1\/20+1\/30+1\/42+1\/56+1\/72求简便方法_百度知 ...
1\/2+1\/6+1\/20+1\/30+1\/42+1\/56+1\/72 =1\/1 ×2+1\/2×3+1\/3×4……+1\/8×9 =（2-1）\/1 ×2+（3-2）\/2×3+（4-3）\/3×4……+（9-8）\/8×9 =1-1\/2+1\/2-1\/3+1\/3-1\/4+……+1\/8-1\/9 =1-1\/9 =8\/9 ....