Question

Sum of n terms of an a.p is sn=3n^2 + 6n.find nth term ?

Answer 1

Given Sn = 3n2  + 6n

S1 = 3×1 + 6×1 = 9

S2 = 3×4 + 6×2 = 12 + 12 = 24 .

Therfore First term a1 = 9 &  Second term a2 = 24 - 9 = 15 and d = 15 - 9 = 6.

Now nth term an = 7 + ( n - 1) 6