1/3×2/5+1/5×2/7+1/7×2/9+1/9×2/11+1/11×2/13 算式

问题描述:

1/3×2/5+1/5×2/7+1/7×2/9+1/9×2/11+1/11×2/13 算式

=1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13
=1/3-1/13
=10/39