Question

S=n/2 [a+(n-1)d]
make a subject​

Answer 1

`s = \frac n 2 (a + (n-1) d)`

`(2s)/(n) = a + (n-1)d`

`(2s)/(n) -(n+1)d = a`

We could expand this further but let's call it done.

Answer: a = 2s/n - (n+1)d