Question

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

Answer 1

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+(n-1)d`

If we substitute the given values we get:

`a_n=-25+(n-1)*15=-25+15n-15`

`a_n=-40+15n`