soft114
幼苗
共回答了131个问题 举报
1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + ... + 1/(2010x2011)
=(1-1/2)+(1/2 - 1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+...+(1/2010-1/2011)
=1-1/2+1/2 - 1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+...+1/2010-1/2011
=1- 1/2011
=2010/2011
1年前
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