1/3+1/15+1/35.+1/195=?

tt秋意2022-10-04 11:39:543条回答

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天天飞ing 共回答了13个问题 | 采纳率84.6%: 原式=1/（1×3）+1/（3×5）+1/（5×7）+..+1/（13×15）
=（1/1-1/3+1/3-1/5+1/5-1/7+.+1/13-1/15）×1/2
=（1-1/15）×1/2
=14/15×1/2
=7/15; 1年前

liming1414 共回答了7个问题 | 采纳率: 1/2*(1-1/3+1/3-1/5+1/5-1/7+.....+1/13-1/15)=1/2*14/15=7/15; 1年前

qiu_yu_han 共回答了4个问题 | 采纳率: 原式=1/1*3+1/3*5+1/5*7+......+1/13*15
=1/2(1-1/3+1/3-1/5+1/5-1/7+......1/13-1/15)
=1/2(1-1/15)
=7/15; 1年前

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