Question

If sum of nth term of an A.P.is 3n×n+5n.find common difference

Answer 1

Sum of nth term,Sn=3n.n+5n
Sum of first Term,S1=3(1.1)+5(1)=8=First term,a
Why?
As,
Sum of 1st term=First term
Sum of first 2 terms,S2=3(2)(2)+5(2)=22=a+a+d
(First term+Second term)

Now,a+a+d=22
8+8+d=22
(Common difference)d=6

Thank You