等差数列an的前n项和为Sn,a3=8,S11=187.求an
人气：389 ℃ 时间：2020-03-28 15:54:41
解答
a3 = 8 = a1 + 2dS11 = 187 = (a1 + a11) * 11 / 2 = (2a1 + 10d) * 11 / 2 = (a1 + 5d) * 11a1 + 5d = 17d = 3a1 = 2an = 2 + 3(n-1) = 3n -1希望我的回答对你有用,望及时采纳为满意答案.
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