请问这道题怎样解算:(1+1/2+1/+L+1/2007)*(1/2+1/3+L+1/2008)-(1+1/2+L+1/2008)*(1/2+1/3+L+1/2007)=

问题描述:

请问这道题怎样解算:(1+1/2+1/+L+1/2007)*(1/2+1/3+L+1/2008)-(1+1/2+L+1/2008)*(1/2+1/3+L+1/2007)=

设1+1/2+1/3+.+1/2008=a
(a-1/2008)(a-1)-a(a-1-1/2008)=1/2008