Question

If sum of n terms of an AP is 3n2 +5n then find its 3rd term.​

Answer 1

Answer:

Sn=3n2+5n

S1=a1=3(1)2+5(1)=8

S2=3(2)2+5(2)=22

S2=22=a1+a2

a2=22-8=14

d=a2-a1=14-8=6

nth term value is 164,then what is n?

nth term=a+(n-1)d

164=8+(n-1)6

164-8 / 6=n-1

156/6=n-1

26+1=n

n=27

So 27thterm is 164.

Answer 2

the given no is 3n2 +5n and we have to find third term so , 3n2 + (+5n) = 8n2