Question

The sum of the first n terms of an ap is 3 n²+6n. p find the nth term and the 15th term of this AP

Answer 1

Answer:

Given Sn = 3n²+6n

So, the sum of first term and the first term both are equal.

So, a1 = S1 = 9

S2 = a1+a2 = 24 → a2 = 15

d = a2-a1 = 6

nth term =a+(n-1)d = 9+(n-1)6 = 6n+3

a15 = 6(15) + 3 = 93

Answer 2

See the above attachment for answer.