Question

if an A.P. the sum of first 'n' terms is 3x^2/2 + 13n/2. find its 25th term.​

Answer 1

Given:

Sn = (3(n^2)/2) + (13n/2)

a25 = S25 - S24

a25 = [(3(25^2)/2) + (13*25/2)] - [(3(24^2)/2) + (13*24/2)]

a25 = (3/2)*[(25)^2 - (24)^2] + (13/2)*[25 - 24]

a25 = (3/2)*(25 + 24)*(25 - 24) + (13/2)*(1)

a25 = (3/2)*(49) + 13/2

a25 = (1/2)*[(3*49) + 13]

a25 = (1/2)*[147 + 13]

a25 = (1/2)*(160)

a25 = 80 ——> Answer

Answer 2

hope this helps you☺️☺️☺️☺️