Question

How do you find the term n=20, given the arithmetic sequence `a_1=-4` and d=-9?

Answer 1

`a_20=-175`. See below

Explanation:

An arithmetic sequence has the general term given by

`a_n=a_1+(n-1)d`

Then applying given values

`a_n=-4+(n-1)(-9)=-4-9n+9=-9n+5`

For `n=20`, we have `a_20=-9·20+5=-175`