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

- math-algebra -
**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.

- math-algebra -
**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.

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