1/2+1/6+1/12+·····+1/90怎么算

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1/2+1/6+1/12+·····+1/90怎么算

1/2+1/6+1/12+·····+1/90怎么算
1/2+1/6+1/12+·····+1/90怎么算

1/2+1/6+1/12+·····+1/90怎么算
1/2+1/6+1/12+·····+1/90
=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

简算 1/2+1/6+1/12+······+1/9900 急·····················1+2+3+...+999=? 1 2 3 4 ·····7 ·······10 ········?1 3 5 7 ·····?······?··········290 1 4 9 ·····?······?··········? 1/2+1/6+1/12+·····+1/90怎么算 变态数学题·······方程一道············x+2y+3z=1x=y+12x+3y+5z=2方程组············要过程············我解了之后总觉得无解····· 纸鹤数量的意义比如说 1只纸鹤,代表······· 2只纸鹤,代表······· ······················· ···························· ·················· 越多越好, 俗语和名句的填空1······,自知之明.2······,行必果.3工欲善其事,······.4临渊羡鱼,······.5非学无以广才,······.6······,福兮祸之所伏.7项庄舞剑,······.8······,人以群 观察1/2 1/6 1/12 1/20 1/30·····的排列顺序,第60个数是多少?观察1/2 1/6 1/12 1/20 1/30··························的排列顺序,第60个数是多少? 证明1·3·5·····(2n-1)/2·4·6·····2n 1-1/2+1/6+1/12+1/20+·········+1/72+1/90巧算 计算1/（1*4）+1/（4*7）+1/（7*10)+------+1/(97*100)································································································ 这几道奥数题谁会,求2014在哪一行那一列 1 2 3 4 5 10 9 8 7 6 11 12 13 14 15 20 19 18 17 16 求2014哪一行那一列 1 2 3 4 5 6 7 8 9 ···· ····· ·························· 2/1+6/1+12/1+20/1+······+9702/1+9900/1 1+2++3+··········+10000= 在等腰三角形ABC中,AB=AC.求证1、∠BAD=∠CAE 2、如果AD=AE,那么BD=CE吗?急啊························································· 8+11+14+17+20+·······+305 数学计算题.呜呜呜1+2+3+4+···················+98+99+100+99+98+···············+3+2+1 1+2+3+4+······+78+79+801/2+1/6+1/12+1/20+······+1/72+1/90100-99+98-97+96-······+4-3+2-11000-1-2-3-4-······-78-79-801/15+2/15+······+13/15+14/15注：例 1/15 就是 十五分之一 将下列每个3*3正方形内的九格以及横竖九格均填入一至九的数字,且不重复.· 8 9 · 2 ··1··· 1 ··· 3······· 6 7········· 8 2·········5 ···· 7 ··············· 9 8 ····7 ·