=2005×(1/1*2+1/2*3+……+1/2004*2005)
=2005×(1-1/2+1/2-1/3+……+1/2004-1/2005)
=2005×(1-1/2005)
=2005×2004/2005
=2004 对吧
=2005×(1/1*2+1/2*3+……+1/2004*2005)
=2005×(1-1/2+1/2-1/3+……+1/2004-1/2005)
=2005×(1-1/2005)
=2005×2004/2005
=2004
1/1乘2+1/2乘3+1/3乘4+..+1/2004乘2005
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+……+(1/2004-1/2005)
=1-1/2005=2004/2005
等于2004,,,