求2/1+6/1+12/1+20/1+30/1+...110/1的和是多少

问题描述:

求2/1+6/1+12/1+20/1+30/1+...110/1的和是多少

=1-1/2+1/2-1/3+1/3-1/4+1/5-1/6+..+1/10-1/11 =1-1/11 =10/11