1/2+1/6+1/12+1/20+1/30+.+1/110=?
问题描述：
1/2+1/6+1/12+1/20+1/30+.+1/110=?
答
1/2+1/6+1/12+1/20+1/30+.+1/110
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+……+1/10-1/11
=1-1/11
=10/11