问题
选择题
等差数列{an}前n项和为Sn，等差数列{bn}前n项和为Tn，而且
|
答案
∵等差数列{an}{bn}的前n项和分别为Sn，Tn，
∵
=Sn Tn
，n n+1
∴
•a10 b9
=a9 b10
•a9 b9
=a10 b10
•s17 T17
=s19 T19
×17 18
=19 20 323 360
故选B．
搜题请搜索小程序“爱下问搜题”
等差数列{an}前n项和为Sn，等差数列{bn}前n项和为Tn，而且
|
∵等差数列{an}{bn}的前n项和分别为Sn，Tn，
∵
=Sn Tn
，n n+1
∴
•a10 b9
=a9 b10
•a9 b9
=a10 b10
•s17 T17
=s19 T19
×17 18
=19 20 323 360
故选B．