2/5+2/45+2/117+2/221=?

来源：学生作业学帮网编辑：学帮网时间：2024/06/17 03:51:30

2/5+2/45+2/117+2/221
=(1-1/5)/2+(1/5-1/9)/2+(1/9-1/13)/2+(1/13-1/17)/2
=[(1-1/5)+(1/5-1/9)+(1/9-1/13)+(1/13-1/17)]/2
=(1-1/17)/2
=8/17