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1/x3+1/2x4+1/3x5+...+1/18x20要列式哟!
人气:220 ℃ 时间:2020-05-06 11:52:28
解答
1/1x3+1/2x4+1/3x5+...+1/18x20
=1/2(1-1/3+1/2-1/4+1/3-1/5+1/4-1/6+.+1/18-1/20)
=1/2(1-1/20)
=19/40
1/1*3=1/2(1-1/3)其他以此类推
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