1003/2005
补充回答:
(1+1/2)(1-1/2)(1+1/3)(1-1/3)(1+1/4)(1-1/4).......(1+1/2004)(1-1/2004)(1+1/2005)(1-1/2005)
=(1+1/2)(1+1/3)(1+1/4).......(1+1/2004)(1+1/2005)X(1-1/2)(1-1/3)(1-1/4).......(1-1/2004)(1-1/2005)
=(3/2)(4/3)(5/4)......(2005/2004)(2006/2005)X(1/2)(2/3)(3/4).....(2003/2004)(2004/2005)
=(2006/2)X(1/2005)
=1003/2005
4 9 16 2004^2 2005^2
.