(1/3+1/4……+1/2006)(1/2+1/3……+1/2006)-(1/2+1/3+……+1/2006)(1/3
(1/3+1/4……+1/2006)(1/2+1/3……+1/2006)-(1/2+1/3+……+1/2006)(1/3
计算:(1/2+1/3+……+1/2006)(1+1/2+1/3+……+1/2005)-
1-2+3-4……+2005-2006
1、(1/2+1/3+……1/1007)*(1+1/2+……1/2006)-(1+1/2+……+1/2007)*(1/2
2008+2007+2006…+3+2+1
巧算:1×(1-1/2)×(1-1/3)×……×(1-1/2005)×(1-1/2006)×(1-1/2007)×(1-
计算:(1/2006-1)(1/2005-1)(1/2004)… (1/3-1)(1/2-1).
(2007-1)+(2006-2)+(2005-3)+……+(1005-1003)
1+2+3+……+2006+2007+2006+.+3+2+1
计算:(1/2+1/3+1/4+…+1//2006)(1+1/2+1/3+…+1/2005)-(1+1/2+1/3+1/
①1/2+1/2*3+1/3*4+…+1/2006*2007=
2008-2007+2006-2005+…+4-3+2-1=