Question

Find the sum of 15th term 3+6+9

Answer 1

Step-by-step explanation:

A.P. - 3,6,9....

Common difference d = 6-3=9-6=3

a_1=3a

1

=3

Formula of nth term = a_n=a+(n-1)da

n

=a+(n−1)d

Substitute n = 15

a_{15}=3+(15-1)3a

15

=3+(15−1)3

a_{15}=3+(14)3a

15

=3+(14)3

a_{15}=45a

15

=45