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1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45+1/55+1/66

结果为(即第一步的结果,第二步的结果依次类推)1/2,3/5,2/3,5/7,3/4,7/9…… 发现规律 1/2,2/3,3/4,的分子分母加1。 3/5,5/7,7/9,的分子分母加2。 加到1/45时,一共出现7个结果,即是奇数个结果,那么应该是1/2,2/3,3/4,4/5中的4/...

1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45 =2*(1/6+1/12+1/20+1/30+1/42+...+1/90) =2*(1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+...+1/9*10) =2*(1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+...+1/9-1/10) =2*(1/2-1/10) =2*2/5 =4/5

1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45 =1/3+1/2*3+1/2*5+1/3*5+1/3*7+1/4*7+1/4*9+1/5*9 =3/2*3+5/2*3*5+7/3*4*7+9/4*5*9 =1/2+1/6+1/12+1/36 =(18+6+3+1)/36 =19/18

1.推荐小学生解题: 找出分母的最大公倍数:1260 1/45=28/1260 1/36=35/1260 1/28=45/1260 1/21=60/1260 1/15=84/1260 1/10=126/1260 1/6=210/1260 1/3=420/1260 分子相加,分母不变。等于1008/1260 =4/5=0.8 2.用电子表格直接计算。

原式=2/(2×3)+2/(3×4)+2/(4×5)+2/(5×6)+……+2/(15×16) =2(1/2-1/3+1/3-1/4+1/4-1/5+……+1/15-1/16) =2×(1/2-1/16) =7/32 如果你认可我的回答,请及时点击采纳为【满意回答】按钮 手机提问者在客户端右上角评价点“满意”即可。 你的采纳是我前进的动...

解:原式=1/3+1/2-1/3+1/3(1/2-1/5)+1/2(1/3-1/5)+1/4(1/3-1/7)+1/3(1/4-1/7)+1/5(1/4-1/9)+1/4(1/5-1/9)+1/6(1/5-1/11)+1/5(1/6-1/11) =1/3+1/2-1/3+1/3*1/2-1/3*1/5+1/2*1/3-1/2*1/5+1/4*1/3-1/4*1/7+1/3*1/4-1/3*1/7+1/5*1/4...

通项为2/(n+1)(n+2)=2(1/(n+1)-1/(n+2))前n项和s=1-2/(n+2)故原式为4/5

1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45 =(1/3+1/6)+(1/10+1/15)+(1/21+1/28)+(1/36+1/45) =(2+1)/6+(3+2)/30+(4+3)/84+(5+4)/180 =1/2+1/6+1/12+1/20 =1/2+(1/2-1/3)+(1/3-1/4)+(1/4-1/5) =1-1/5 =4/5

3+6+10+15+21+28+36+45 =164 1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45 =77/105

1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45 =2*(1/6+1/12+1/20+1/30+1/42+...+1/90) =2*(1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+...+1/9*10) =2*(1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+...+1/9-1/10) =2*(1/2-1/10) =2*2/5 =4/5

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