Question

How do I find the partial sum of an arithmetic sequence?

Answer 1

`color(purple)(S_n = n/2 * (2a + (n-1)d)`

Explanation:

First term is a, common difference is d

`n^(th)` `term` `a_n = a + (n-1) * d`

Partial sum of an arithmetic sequence is given by

`S_n = n / 2 * (a + a_n) = n/2 * (a + (a + (n-1) * d)`

`color(purple)(S_n = n/2 * (2a + (n-1)d)`