### Home > GB8I > Chapter 11 Unit 12 > Lesson INT1: 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 $a$ sub $n=−225$ and solve for $n$.