因为 x/(n*(n+1)) = x/n - x/(n+1)
所以原式展开可得：
(x - x/2) + (x/2 - x/3) + ... + (x/2005 - x/2006)
= x - x/2006
= 2005x/2006
因为2005x/2006 = 2005
所以x = 2006
谢谢采纳 ^_^