Question

In an A.P the sum of first n terms is 3n2/2+13n/2 find its second terms

Answer 1

sn=n/2[2*a+(n-1)*d]
or,3n^2/2+13n/2=n/2[2*a+(n-1)*d]
or,n/2[3n +13]=n/2[2*a+(n-1)*d]
3n+13=2a+(n-1)*d