Question

the sum of first 'n' term of an AP is given by the formula Sn=3n2+n then its 3rd term​

Answer 1

Answer:

I hope it is helpful for you

Answer 2

given, Sn = 3n² +n

put n=1

S1 = 3×1² +1 =4

but, s1 = A1

put n = 2

S2 = 3×2²+2 = 14

now A2 = S2 - A1 _________(S2 = A1 +A2 )

A2 = 14-4 = 10

now common difference d = A2 - A1 = 10-4 = 6

we got

d=6

A1 = 4

and

An = A1 + (n-1)d

A3 = 4 + (3-1)6

A3 = 4 + 2(6)

A3 = 4+12= 16

so the third term of AP is 16