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 ...