### Home > A2C > Chapter 12 > Lesson 12.1.1 > Problem 12-20

12-20.

A series has 9 terms, the last term is 18, and the fifth term is 6. What is the series? Homework Help ✎

Find the sequence that corresponds to the terms of the series.

*t*(5) = 6 = (5)*a* + *b**t*(9) = 18 = (9)*a* + *b*

*a* = 3 and *b* = −9

Now use the sequence to find the rest of the terms of the series.

(−6) + (−3) + 0 + 3 + 6 + 9 + 12 + 15 + 18