Question

If sum of n terms of an ap if sn = 3n^2 + 2n^2.the common difference of ap is

Answer 1

Given
sum of.A.P Sn = 3n^3 + 2n^2

let ,Tn = 3n^3 + 2n^2 -----(1)


put" n" = 1, 2, 3.......in(1)

first term ,T1 = 3(1)^3 +2 (1)^2 = 5

T 1 = 5

now put "n = 2 ,we get

T 2 = 24 + 8 = 32

T 2 = 32

put ,n = 3 in (1)

T 3 = 81 + 18 = 99

common difference (d)

= (T 3 - T 2) - ( T 2 - T 1 )

= ( 99 - 32 ) - ( 32 - 5 )

= 67 - 27

= 40

hence, common difference of A.P (d )= 40


【hope it helps】