Question

The sum of first n terms of an ap is 3n2 + 4n. Find the nth term of this ap

Answer 1

S1=3×1×1+4×1

=7=a1

S2=3×2×2+4×2

=12+8

=20

a2=S2-S1

=13

an=a+(n-1)d

common Difference=a2-a1

=6

an=7+6n-6

=1+6n

Answer 2

See the above attachment for answer.