1x1/2+1/2x1/3+1/3x1/4+1/4x1/51/2009x1/2010怎么做啊

问题描述:

1x1/2+1/2x1/3+1/3x1/4+1/4x1/51/2009x1/2010怎么做啊

原式=(1-1/2)+(1/2-1/3)+(1/3-1/4)+……+(1/2009-1/2010)=1-1/2010=2009/2010

原式=(1-1/2)+(1/2-1/3)+(1/3-1/4)+.+(1/2009-1/2010) =1-1/2010 =2009/2010 OK?