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+·····+1/9
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
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