Question

The sum of first n terms of an AP is 3n^2+6n. Find the nth term of this AP. It's urgent plzzzz!!

Answer 1

Sn = 3n^2 + 6n

S1 = 3.1^2 + 6.1 = 9 = t1

S2 = 3.2^2 + 6.2 = 24 = t1 + t2

S2 - S1 = t2 + t1 - t1 = t2 = 24 - 9 = 15

d = t2 - t1 = 15 - 9 = 6

tn = 9 + (n - 1)6 = 6n + 3