(2/343+4/343+6/343+…+98/343)-(3/686+5/686+7/686+…+99/686) ……答案是3.5
来源:学生作业帮助网 编辑:作业帮 时间:2024/08/31 23:56:53
![(2/343+4/343+6/343+…+98/343)-(3/686+5/686+7/686+…+99/686) ……答案是3.5](/uploads/image/z/7105633-25-3.jpg?t=%282%2F343%2B4%2F343%2B6%2F343%2B%E2%80%A6%2B98%2F343%29-%283%2F686%2B5%2F686%2B7%2F686%2B%E2%80%A6%2B99%2F686%29+%E2%80%A6%E2%80%A6%E7%AD%94%E6%A1%88%E6%98%AF3.5)
(2/343+4/343+6/343+…+98/343)-(3/686+5/686+7/686+…+99/686) ……答案是3.5
(2/343+4/343+6/343+…+98/343)-(3/686+5/686+7/686+…+99/686) ……答案是3.5
(2/343+4/343+6/343+…+98/343)-(3/686+5/686+7/686+…+99/686) ……答案是3.5
(2/343+4/343+6/343+…+98/343)-(3/686+5/686+7/686+…+99/686)
= (4/686+8/686+12/686+...+196/686)-(3/686+5/686+7/686+…+99/686)
=4/686-3/686+8/686-5/686+12/686-7/686+...+196/686-99/686
=1/686+3/686+5/686+...+97/686
=[(1+97)x49/2]/686 (分子是1为首相 97为末项 2为方差的等差数列 共49项)
=7/2
=3.5
不懂继续问哦^_^
原式=4/686+8/686+……+196/686-3/686-5/686-……-99/686
=4/686-3/686+8/686-5/686+12/686-7/686+……+196/686-99/686
=1/686+3/686+5/686+……+97/686
=[(1+97)×49/2]/686
=49×49/686
=3.5
=(49*100/343)/2-(49*102/686)/2
=49*(200/686-102/686)/2
=49/14
=3.5 这种方法你们老师应该有教过