Question

The sum of the first n terms of an AP is 5n² − n. Find the n^th term of the AP.

Answer 1

As, S_n = 5n² – n

Now, n^th term is given by a_n = S_n – S_{n – 1}

a_n = [5n² − n] – [5(n − 1)² − (n − 1)]

a_n = 5[n² − (n − 1)²] – [n – (n – 1)]

a_n = 5[2n – 1] – [1]

a_n = 10n – 6