已知公差不为0的等差数列{an}满足a1,a3,a4成等比数列,Sn为数列{an}的前n项和,则的值为( )... 问题详情：已知公差不为0的等差数列{an}满足a1,a3,a4成等比数列,Sn为数列{an}的前n项和,则的值为()A.-2 B.-3 C.2 ...
