如果a=1,b=1,那么1/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+……+1/(a+2004)(b+2004)值是多少
问题描述：
如果a=1,b=1,那么1/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+……+1/(a+2004)(b+2004)值是多少
答
是a=1,b=2吧
那么
原式=1/(1x2)+1/(2x3)+1/(3x4)+.+1/(2004x2005)
=1-1/2+1/2-1/3+1/3-1/4+.+1/2004-1/2005
=1-1/2005
=2004/2005