Question

the sum of first n terms of an is 3n2 + 6n find the nth term of this ap

Answer 1

here a1 = a = s1 = 9
a1+ a2 =s2 = 24
a2 = 24-9=15
so d =a2-a1 = 15-9=6
nth term = a+ (n-1)d
=9+(n-1)6
=3+6n

Answer 2

See the above attachment for answer.