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已知1-1/2+1/3-1/4+1/5-...-1/1318+1/1319=a/b,a与b互质,证明a能被1979整除
人气:191 ℃ 时间:2020-01-24 18:11:41
解答
S=1-1/2+1/3-1/4+1/5-...-1/1318+1/1319=(1+1/2+1/3+1/4+...+1/1319)-2*(1/2+1/4+...+1/1318)=(1+1/2+1/3+1/4+...+1/1319)-(1+1/2+...+1/659)=1/660+1/661+...+1/13191/660+1/1319=1979/(660*1319),1/661+1/1318=197...
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