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：作业帮时间：2024/11/16 16:34:19

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