Question

the sum of 1st n terms of an AP is given by the formula Sn=3n^2+n, then its 3rd term is ​

Answer 1

To Find:

find it's 3rd term?

solution:

given that:

=the sum of first n term of ap is sn =3n 2+ n....=1)

=put n=1 in 1 (then)

=S1=3(1)+1

=S1=3(1)+1

=S1=3+1

=S1= 4

=First term of A.p = 4

Now,

put n=2 in 1 then

=S2=3(2)+2

=S2=3(4)+2

=S2=14

=Sum of first two term = 14

=First term + second term =14

=4+ second term =14

=Second term = 14-4

= second term =10

Now we have first term=a=4

second term =10 common difference

=a=10-4=6

common difference =6

Third term Ap = an = a+( n-1) d

=a3=4+(3-1)=6

=a3=4+2(6)

=a3=4+12

=a3=16

Ans;

the third term of the given Ap for the

given problem is 1 .

Used formula;

the general term of an Ap = an = a+( n-1) = d

A= first term

D = Common different

N= Number of terms

I hope it's helpful .

So Mark as brain list.

Answer 2

see the above attachment...