Find the sum of n terms of the series whose nth terms is
(ii) `n^(2)+3^(n)`.

Explanation

We have, `T_(n)=n^(2)+3^(n)`
`" S_(n)= sumT_(n) =sumn^(2)+sum3^(n)`
`=sumn^(2)+(3^(1)+3^(2)+3^(3)+"...."+3^(n))`
`=(n(n+1)(2n+1))/(6)+(3(3^(n)-1))/((3-1))`
`=(n(n+1)(2n+1))/(6)+(3)/(2)(3^(n-1))`