Question

The sum of the first n terns of an Ap is (3n2+6n).Find the nth tern and the 15th tern of this Ap.

Answer 1

Answer:

s1=9

S2=24

S3=45.........by putting the values in sum of first n terms...

so t1=9

t2=15

t3=21

so a=9 and d=6

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

=9+6n-6= 3+6n

and hence......

fifteenth term=a+14d=9+14*6=9+84=93