裂项法:
1/1x3+1/2x4+1/3x5+…+1/2011x2013+1/2012x2014
=1/2×(1-1/3+1/2-1/4+1/3-1/5+……+1/2011-1/2013+1/2012-1/2014)
=1/2×(1+1/2-1/2013-1/2014)
=1/2×6077246/4054182
=3038623/4054182
裂项法:
1/1x3+1/2x4+1/3x5+…+1/2011x2013+1/2012x2014
=1/2×(1-1/3+1/2-1/4+1/3-1/5+……+1/2011-1/2013+1/2012-1/2014)
=1/2×(1+1/2-1/2013-1/2014)
=1/2×6077246/4054182
=3038623/4054182