S6S7S5的知识精选

若等差数列{an}的前n项和为Sn,若S6>S7>S5,则满足SnSn+1<0的正整数n的值...
问题详情:若等差数列{an}的前n项和为Sn,若S6>S7>S5,则满足SnSn+1<0的正整数n的值为()A.10                             B.11C.12                             ...
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