作者spicee ()
看板GMAT
標題[計量] pp1-ps-108
時間Fri Apr 24 21:14:34 2009
In a arithmetic sequence t1,t2,t3,....tn,...,t1=23 and tn=tn-1-3 for each n>1,
what is the value of n when tn=-4?
(A)-1 (B)7 (C)10 (D)14 (E)20
The answer is (C) ,but why?
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1F：推 trpnomad:我想你應該看錯題目了? 04/24 21:26
2F：→ spicee:對 應該是tn=t(n-1)-3 謝謝! 04/24 22:21
3F：推 Alice1027:是一個首項23且公差為-3的等差數列 04/24 22:40
4F：→ Alice1027:-4=23+(n-1)*-3 → n=10 04/24 22:41