### Home > INT1 > Chapter 11 > Lesson 11.1.3 > Problem11-33

11-33.

How many terms are in the arithmetic sequence shown below?

$15,\ 7,\ −1,\ −9,...,\ −225$

Write an equation for the arithmetic sequence using $a_n−m\left(n-1\right)+a_1$

Let $a_n=−225$ and solve for $n$.