1/1*3+1/3*5+1/5*7+.+1/2009*2011
=1/2(1-1/3+1/3-1/5+```+1/2009-1/2011)
=1/2(1-1/2011)
=1/2x2010/2011
=1005/2011
你的题目最后应该打错了,