已知数列{an}的前n项和Sn=n2-9n,若5<ak<8,则k等于 A.9 B. 发布时间:2017-05-03 02:34 │ 来源:www.tikuol.com 题型:选择题 问题: 已知数列{an}的前n项和Sn=n2-9n,若5<ak<8,则k等于A.9 B.8C.7 D.6
题型:选择题 — Congratulations! Your English teacher told me you got an A this time. — Thank you. She is very . [ ]A. impressed B. embarrassed C. terrified D. frustrated 查看答案