(1) find the sum of n term of n(n+1)-2

find the sum of n terms: a(n) = n(n+1)-2

If the n^(th) term of an A.P.is (2n+1), find the sum of first n terms of the A.P.

For the series sum t_(n,) S_n=sum_(n=1)^nt_n=2t_n-1 . Is the series geometric ? If so, find the sum to n terms of the series.

If the sum of n terms of an AP is n^2-2n then find its n^(th) term

find the sum of n terms of the series (4-(1)/(n))+(4-(2)/(n))+(4-(3)/(n))+

The sum of n terms of an A.P.is an (n-1). Find the sum of the squares of these terms.

Find the sum of 'n' terms of an A.P. whose nth term is 2n+1.

Find the sum of n terms of an A.P. whose nth term is (2n+1).

The nth term of a series is 3^(n)+2n; find the sum of first n terms of the series.

Find the sum of first n terms of an AP whose n^(th) term is 5-6n .find the sum of its first 20 terms