Question

(1/2+1/3+1/4+.+1/2004)(1+1/2+.+1/2004)-(1+1/2+.+1/2005)(1/2+

Answer 1

设 1/2+1/3+1/4+.+1/2004 = n,则

原式

= n(1+n)-(1+n+1/2005)n

= n(1+n-1-n-1/2005)

= -n/2005

(题目似乎有误,请再确认一下)