The sum to nth term of an arithmetic seqquence is n2 - 3n. Find the general term.
thanks
sequence question
2008-09-11 9:51 pm
回答 (1)
2008-09-11 11:53 pm
✔ 最佳答案
Let the 1st term be a and the common difference be d. Therefore,put n = 1, sum = 1 - 3 = -2. So a = -2.
Put n = 2, sum = 4 - 6 = -2. So a + a + d = -2, that is -4 + d = -2, so d = 2.
Therefore, the general term is -2 + 2(n - 1) = -2 + 2n - 2 = 2n - 4 = 2(n -2).
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