Question

How do you find the term n=81, given the arithmetic sequence `a_1=20` and d=4?

Answer 1

`81^(st)` term of the arithmetic sequence is `340`.

Explanation:

`n^(th)` term of an arithmetic sequence, whose first term is `a_1` and common difference is `d` is

`a_1+(n-1)xxd`

As we have `a_1=20` and common difference is `d=4`

`81^(st)` term of the arithmetic sequence is

`20+(81-1)xx4=20+80xx4=20+320=340`