# How do you find the explicit formula for the following sequence -25, -10, 5, 20,...?

Mar 26, 2018

See explanation.

#### Explanation:

You can easily see that every term of this sequence comes from adding $d = 15$ to the previous one, and the first term is ${a}_{1} = - 25$. So the general formula is:

## ${a}_{n} = {a}_{1} + \left(n - 1\right) d$

If we substitute the given values we get:

${a}_{n} = - 25 + \left(n - 1\right) \cdot 15 = - 25 + 15 n - 15$