问题标题：
求证1/(n+1)+1/(n+2)+.+1/(3n+1)>1[n属于N*]
问题描述：
求证1/(n+1)+1/(n+2)+.+1/(3n+1)>1[n属于N*]
段世梅回答：
1/(n+1)+1/(3n+1)>2/(2n+1)
1/(n+2)+1/(3n)>2/(2n+1)
.
1/(2n)+1/(2n+2)>2/(2n+1)
1/(2n+1)=1/(2n+1)
1/(n+1)+1/(n+2)+.+1/(3n+1)>(2n+1)/(2n+1)=1
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