Question

if the sum of n terms of A.P is 3n2 + 5n then which of its term is 164 ​

Answer 1

Answer:

Let,

Sn denote the sum of n terms and an be the nth term of the given AP. Then,

Sn=3n²+5n

Sn−1=3(n−1)²+5(n−1)

=3n²−n−2

Now, an=Sn−Sn−1

an=(3n²+5n)−(3n²−n−2)

an=6n+2

Now, am=164

6m+2=164

6m=162

m=27