Question

S=n(a1+an)/2 gives the partial sum of an arithmetic sequence. What is the formula solved for an?

Answer 1

Just took the quiz.

The answer is an=2S-a1n/n

Answer 2

The given formula is

`S= (n)/(2) (a_(1)+a_(n))`

Multiply each side by 2.

`2S=n(a_(1)+a_(n))`

Divide each side by n.

`(2S)/(n) =a_(1) + a_(n)`

Subtract a₁ from each side.

`(2S)/(n) - a_(1) = a_(n)`

Answer:
`a_(n) = (2S)/(n) - a_(1)`