1*3/1+3*5/1+5*7/1+```+2009*2011/1
问题描述：
1*3/1+3*5/1+5*7/1+```+2009*2011/1
答
=(1/2)×[2/1×3+2/3×5+2/5×7+...+2/2009×2011]=(1/2)×[(1/1-1/3)+(1/3-1/5)+(1/5-1/7)+...+(1/2009-1/2011)]=(1/2)×(1-1/3+1/3-1/5+1/5-1/7+...+1/2009-1/2011)=(1/2)×(1-1/2011)=(1/2)×(2010/2011)=1005/20...