已知等差数列{an}的公差是2,其前4项和是-20,则a2=______. 发布时间:2017-04-30 07:23 │ 来源:www.tikuol.com 题型:填空题 问题: 已知等差数列{an}的公差是2,其前4项和是-20,则a2=______.
题型:填空题 The speaker ________have criticized the paraprofessionals, knowing full well that they were seated in the audience.A.should not toB.must notC.ought not toD.may not 查看答案