Question

The formula S=n(a1+an)/2 gives the partial sum of an artithmetic sequence what is the formula solved for an?

Answer 1

S = n(a1 + an)/2

2S = n(a1 + an)

2S = na1 + nan

nan = 2S - na1

an = (2S - n a1)/n

Explanation:

hope it's right