166*167分之166 =(167-1)×166/167=1-166/167=1/1671/2+1/6+1/12+1/20+1/30+1/42+1/56 =1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8=1-1/8=7/81998*（1/11-1/2009）+11*（1/1998-1/2009 ）-2009*（1/11+...