Question

first term of ap if Sn= n² +2n is ​

Answer 1

First term of the AP can be found out by substituting n=1 because the sum of 1st term and the 1st term will be same.

So,

$S_{n} =n^{2} +2n$

$S_{1} =1^{2} +2(1)$

$S_{1} =3$

Hence, first term will be 3.