作业帮1/2+1/6+1/12+1/20+1/30+1/42+1/56
来源：学生作业帮助网 编辑：作业帮 时间：2024/04/28 05:59:17
1/2+1/6+1/12+1/20+1/30+1/42+1/56
1/2+1/6+1/12+1/20+1/30+1/42+1/56
1/2+1/6+1/12+1/20+1/30+1/42+1/56
1/2+1/6+1/12+1/20+1/30+1/42+1/56
=1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+1/7*8
=(1-1/2)+(1/2-1/3)+...+(1/7-1/8)
=1-1/8
=7/8