Question

If the sum of first n terms of an ap if sn is equal to 5n²+3n

Answer 1

if the sum of first n terms of an AP is 5n^2+3n
put n=1,
5(1)^2+3(1)
5+3=8
and put n=2
5(2)^2+3(2)
20+6=26
a2=Sn2-Sn1
a2=26-8
a2=18
so series is 8,18,.................