In the arithmetic sequence {an}, if A1 ＜ 0, S9 = S12, then n is equal to___ The minimum value of Sn is obtained

In the arithmetic sequence {an}, if A1 ＜ 0, S9 = S12, then n is equal to___ The minimum value of Sn is obtained

From the meaning of the question, we can get that s12-s9 = A10 + a11 + A12 = 3a11 = 0, ∵ a11 = 0 and ∵ in the arithmetic sequence {an}, A1 ＜ 0, ∵ an} is arithmetic sequence, and the first 10 items are negative, the 11th item is 0, it is positive from the 11th item, and the sum of the first 10 items or the first 11 items of the ∵ sequence is the smallest, even if the SN smallest serial number n is 10 or 11, so the answer is: 10 or 11