1/2+1/6+1/12+1/20+1/36+1/42+1/56=?
问题描述:
1/2+1/6+1/12+1/20+1/36+1/42+1/56=?
答
1/2+1/6+1/12+1/20+1/36+1/42+1/56
=1-1/2+1/2-1/3+...+1/7-1/8
=1-1/8
=7/8