设等差数列{an}前n项和为Sn(1)若a4=-15 d=3,求Sn的最小值设等差数列{an}前n项和为Sn,(1)若a4=-15,d=3,求Sn的最小值 (2)若a2=9 s4=40且{根号Sn+c}成等差数列,求c的值
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![设等差数列{an}前n项和为Sn(1)若a4=-15 d=3,求Sn的最小值设等差数列{an}前n项和为Sn,(1)若a4=-15,d=3,求Sn的最小值 (2)若a2=9 s4=40且{根号Sn+c}成等差数列,求c的值](/uploads/image/z/1999067-59-7.jpg?t=%E8%AE%BE%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%7Ban%7D%E5%89%8Dn%E9%A1%B9%E5%92%8C%E4%B8%BASn%281%29%E8%8B%A5a4%EF%BC%9D-15+d%EF%BC%9D3%2C%E6%B1%82Sn%E7%9A%84%E6%9C%80%E5%B0%8F%E5%80%BC%E8%AE%BE%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%7Ban%7D%E5%89%8Dn%E9%A1%B9%E5%92%8C%E4%B8%BASn%2C%EF%BC%881%EF%BC%89%E8%8B%A5a4%EF%BC%9D-15%2Cd%EF%BC%9D3%2C%E6%B1%82Sn%E7%9A%84%E6%9C%80%E5%B0%8F%E5%80%BC+%EF%BC%882%EF%BC%89%E8%8B%A5a2%EF%BC%9D9+s4%EF%BC%9D40%E4%B8%94%7B%E6%A0%B9%E5%8F%B7Sn%2Bc%7D%E6%88%90%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%2C%E6%B1%82c%E7%9A%84%E5%80%BC)
设等差数列{an}前n项和为Sn(1)若a4=-15 d=3,求Sn的最小值设等差数列{an}前n项和为Sn,(1)若a4=-15,d=3,求Sn的最小值 (2)若a2=9 s4=40且{根号Sn+c}成等差数列,求c的值
设等差数列{an}前n项和为Sn(1)若a4=-15 d=3,求Sn的最小值
设等差数列{an}前n项和为Sn,(1)若a4=-15,d=3,求Sn的最小值 (2)若a2=9 s4=40且{根号Sn+c}成等差数列,求c的值
设等差数列{an}前n项和为Sn(1)若a4=-15 d=3,求Sn的最小值设等差数列{an}前n项和为Sn,(1)若a4=-15,d=3,求Sn的最小值 (2)若a2=9 s4=40且{根号Sn+c}成等差数列,求c的值
按作业格式
1 由a4=-15 d=3 得 an= nd -27
所以 要Sn最小 则 an