Question

Let there be an A.P.with first term 'a' common difference 'd'.If a_(n) denotes its n^( th ) term and S_(n) th of first n terms find.k if S_(n)=3n^(2)+5n and a_(k)=164​

Answer 1

Answer:

If a_(n) denotes its n^( th ) term .

S(k)   =   3k^(2)+5k  

 

3k+5   =  1/2 ( a1+164)