Question

in an a.p the sum of n terms is 3xsquare/2+13x/2 find 25th term​

Answer 1

$S_{n} =3x^{2} /2 +13x/2$

$S_{1}=3/2+13/2 = 16/2=8\\S_{2}=12/2+26/2=19$

As we know

$S_{1}=a_{1}\\S_{2}-S_{1}= a_{2}$

Thus first term=8 , second term =19-8=11

thus common difference= 11-8 = 3

Thus the 25 term by using the formula

$a_{n} =a+(n-1)d$

25 term = 8+24(3)

Thus the 25th term is = 80