1/1x3+1/3x5+1/5x7.1/2009x2010+1/2011x2013
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1/1x3+1/3x5+1/5x7.1/2009x2010+1/2011x20131/1x3+1/3x5+1/5x7.1/2009x2010+1/2011x20131/1x3+1/3x5+1/5x7.
1/1x3+1/3x5+1/5x7.1/2009x2010+1/2011x2013
1/1x3+1/3x5+1/5x7.1/2009x2010+1/2011x2013
1/1x3+1/3x5+1/5x7.1/2009x2010+1/2011x2013
1/1x3+1/3x5+1/5x7.1/2009x2011+1/2011x2013
=1/2×﹙1－1/3+1/3-1/5······+1/2009-1/2011+1/2011-1/2013)
=1/2×﹙1-1/2013﹚
=1006/2013