1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90(写过程)

来源：学生作业帮助网编辑：六六作业网时间：2024/06/12 16:20:57

1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90(写过程)1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90(写过程)1/2+1/

1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90(写过程)
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90(写过程)

1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90
=1-1/2+1/2-1/3+1/3-1/4+......1/9-1/10
=1-1/10
=9/10