Question

If sum of n term of an ap is 2n2 +5n then find nth term

Answer 1

nth term = sum of n terms - sum of n-1 terms.
i.e., Tn = Sn - Sn-1
Therefore Tn =
$= (2 {n}^{2} + 5n) - (2 {(n - 1)}^{2} + 5(n - 1)) \\ = 2 {n}^{2} + 5n - (2 {n}^{2} - 4n + 2 + 5n - 5) \\ = 4n + 3$