2楼lh312151
(......)
发表于 2008-11-23 13:21
只看此人
A=1-1/2+1/3-1/4+……+1/1993-1/1994
=1+1/2+1/3+1/4+……+1/1993+1/1994-2(1/2+1/4+1/6+……+1/1994)
=1+1/2+1/3+1/4+……+1/1993+1/1994-(1+1/2+1/3+……+1/997)
=1/998+1/999+……+1/1994
B=1/1996+1/1998+1/2000+……+1/3988
=(1/2)*(1/998+1/999+……+1/1994)
所以A/B=2.