### Home > A2C > Chapter 13 > Lesson 13.2.3 > Problem 13-135

13-135.

Each of the following sums is the beginning of an arithmetic series. Find the

*n*^{th}term of each series, for the specified value of*n*. Homework Help ✎(−2) + (−5) + (−8) + …,

*n*= 129 + 15 + 21 + …,

*n*= 20

Set up an equation to describe the sequence.

*t*(*n*) = −2 − 3(*n* − 1)

Now substitute 12 for *n* to find the 12th term.

*t*(12) = −2 − 3(11)

−35

See part (a).