1/1x3+1/3x5+1/5x7+...1/2009x2011+1/2011×2013
=(1-1/3+1/3-1/5+1/5-1/7+...+1/2011-1/2013)÷2
=(1-1/2013)÷2
=2012/2013÷2
=1006/2013大哥，一定对吗？