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等差数列{an}的前n项和为Sn,公差d<0.若存在正整数m(m≥3),使得am...
等差数列{an}的前n项和为Sn,公差d<0.若存在正整数m(m≥3),使得am=Sm,则“n>m(n∈N*)”是“Sn<an”的( )
A.既不充分也不必要条件
B.充分不必要条件
C.必要不充分条件
D.充要条件
考点分析:
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