# How do you write an equation for the nth term of the arithmetic sequence: -3, -5, -7, -9, ...?

Oct 30, 2016

${a}_{n} = - 2 n - 1$

#### Explanation:

The formula for an arithmetic sequence is ${a}_{n} = {a}_{1} + \left(n - 1\right) d$
where ${a}_{1}$ is the first term and $d$ is the difference between terms.

In this case ${a}_{1} = - 3$ and $d = - 2$

${a}_{n} = - 3 + \left(n - 1\right) \left(- 2\right) = - 3 - 2 n + 2 = - 2 n - 1$

${a}_{n} = - 2 n - 1$