设等差数列{an}的公差为d,若数列{}为递减数列,则( )(A)d>0 (B)d<0(C)a1...
问题详情：设等差数列{an}的公差为d,若数列{}为递减数列,则()(A)d>0 (B)d<0(C)a1d>0(D)a1d<0【回答】D解析:由{}为递减数列,知{a1an}为递减数列,a1an=a1[a1+(n-1)d]=a1dn+a1(a1-d),∴a1d<0.故选D.知识点：数列题型：选择题...
问题详情：设等差数列{an}的公差为d,若数列{}为递减数列,则()(A)d>0 (B)d<0(C)a1d>0(D)a1d<0【回答】D解析:由{}为递减数列,知{a1an}为递减数列,a1an=a1[a1+(n-1)d]=a1dn+a1(a1-d),∴a1d<0.故选D.知识点：数列题型：选择题...