1/2X1/3-1/3X1/4-1/4X1/5-1/5X1/6.-1/39X1/40

紫姬粉丝团2022-10-04 11:39:542条回答

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北大荒BJ 共回答了17个问题 | 采纳率100%
1/2X1/3=1/2--1/3
1/3X1/4=1/3--1/4
.
依次类推最后结果=1/2--1/140=69/140
1年前
rayhou 共回答了1个问题 | 采纳率
1111
1年前

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解析:原式分子为1+3+5+…+(2x-1)
=
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2=x2
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x2

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故答案为案:10

点评:
本题考点: 数列的求和.

考点点评: 本题考查了数列求和的两个常用方法:公式法、裂项求和,裂项求和时注意公式[1n(n+k)=1/k•(1n −1n+k)中的1k]不要漏掉.

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