1/2+1/6+1/12+1/20+1/30+1/42=

来源：学生作业帮助网编辑：六六作业网时间：2024/11/24 22:13:04

1/2+1/6+1/12+1/20+1/30+1/42=1/2+1/6+1/12+1/20+1/30+1/42=1/2+1/6+1/12+1/20+1/30+1/42==1/1×2+1/2×3+1/3

1/2+1/6+1/12+1/20+1/30+1/42=
1/2+1/6+1/12+1/20+1/30+1/42=

1/2+1/6+1/12+1/20+1/30+1/42=
=1/1×2+1/2×3+1/3×4+1/4×5+1/5×6+1/6×7
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-1/7
=6/7