求1/1×4+1/4×7+1/7×10+…+1/2008×2011的值,公式是1/n(n+3)=1/3(1/n-1/n+
2个回答
1/1×4+1/4×7+1/7×10+…+1/2008×2011
=1/3×(1-1/4+1/4-1/7+……+1/2008-1/2011)
=1/3×2010/2011
=670/2011
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