(1/2)+(1/6)+(1/12)+(1/20)+(1/30)+.+(1/420)
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解决时间 2021-01-30 12:48
- 提问者网友:趣果有间
- 2021-01-29 12:43
(1/2)+(1/6)+(1/12)+(1/20)+(1/30)+.+(1/420)
最佳答案
- 五星知识达人网友:患得患失的劫
- 2021-01-29 13:07
(1/2)+(1/6)+(1/12)+(1/20)+(1/30)+.+(1/42)=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======以下答案可供参考======供参考答案1:(1/2)+(1/6)+(1/12)+(1/20)+(1/30)+......+(1/420)=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)+......+1/(20*21)=1-1/2+1/2-1/3+1/3-1/4+1/4-15+1/5-1/6+....+1/20-1/21=1-1/21=20/21不懂可追问满意请采纳谢谢供参考答案2:(1/2)+(1/6)+(1/12)+(1/20)+(1/30)+......+(1/420)=(1/1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+......+(1/20-1/21)=1-1/21=20/21供参考答案3:原式=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+···+1/20-1/21 =1-1/21 =20/21供参考答案4:可以简算,化为:1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+......+1/60-1/70=1-1/70=69/70供参考答案5:解由1/2=1-1/21/6=1/2-1/31/12=1/3-1/41/20=1/4-1/51/30=1/5-1/6...............................1/380=1/19-1/201/420=1/20-1/21即(1/2)+(1/6)+(1/12)+(1/20)+(1/30)+......+(1/420)=(1-1/2)+(1/2-1/3)+(1/3-1/4)+.....+(1/19-1/20)+(1/20-1/21)=1-1/21=20/21供参考答案6:(1/2)+(1/6)+(1/12)+(1/20)+(1/30)+......+(1/420)=1/2+1/(2×3)+1/(3×4)+1/(4×5)+......+1/(20×21)=1/2+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+.....+(1/20-1/21)=1-1/21=20/21供参考答案7:(1/2)+(1/6)+(1/12)+(1/20)+(1/30)+......+(1/420)=1/(1×2)+1/(2×3)+1/(3×4)+……+1/(20×21)=(1/1-1/2)+(1/2-1/3)+(1/3-1/4)+……+(1/20-1/21)=1-(1/2-1/2)-(1/3-1/3)-……-(1/20=1/20)-1/21=1-1/21=20/21
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- 1楼网友:旧脸谱
- 2021-01-29 14:15
这个问题的回答的对
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