Question

if sum of n terms of a series be 3nsquare + 5n find its 10th term

Answer 1

If you know Sn then Tn is given by the formula (Sn)-(Sn-1).
so now since we want T10 we require to do
T10= (S10) - (S9)
=( 3*10^2 + 5*10) - (3*9^2 + 5*9)
=350 - 288
=62

Answer 2

3n² + 5n

if we substitue n = 1, we will get 1st term.

3(1)² + 5(1)
= 3 + 5 
= 8

n=2 - first term we get second term.

3(2)² + 5(2)
12 + 10
=22

sum of 2 terms = 22
second term = 22-8
= 14

common difference = second term - first term
= 14 -8 
d = 6 

now 10th term common formula = a + 9d
10th term = 8 + 9(14)
=8 + 126
= 134 

134 is the 10th term.


hope it helps!!!!!