Posted by Anonymous on Wednesday, September 26, 2007 at 1:16am.
14. The last term of an arithmetic sequence is 207, the common difference is 3, and the number of terms is 14. What is the first term of the sequence?:
A. 165
B. 171
C. 249
D. 168
Please explain. thanks

mathalgebra  PsyDAG, Wednesday, September 26, 2007 at 12:21pm
Subtract the difference from the last term 13 times, since the last term is the 14th number. Can you think of a faster way to do this?
I hope this helps. Thanks for asking. 
mathalgebra  tchrwill, Wednesday, September 26, 2007 at 2:16pm
The last term of an arithmetic sequence is 207, the common difference is 3, and the number of terms is 14. What is the first term of the sequence?:
A. 165
B. 171
C. 249
D. 168
Please explain. thanks
The last, or nth, term of an arithmetic progression is defined by L = a + (n  1)d where L = the last term, a = the first term, n = the number of terms and d = the common difference.
Therefore, 207 = a + (14  1)3
...............= a + 39
Therefore, a = 207  3396 = 168.