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

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

If the n^(t h) term of an A.P. is 2n+1 , then the sum of first n terms of the A.P. is n(n-2) (b) n(n+2) (c) n(n+1) (d) n(n-1)

If the n^(t h) term of an A.P. is 2n+1 , then the sum of first n terms of the A.P. is n(n-2) (b) n(n+2) (c) n(n+1) (d) n(n-1)

If the sum of the first four terms of an AP is 40 and the sum of the first fourteen terms of an AP is 280. Find the sum of first n terms of the A.P.

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

In the A.P. nth term of an A.P. is given by (-4n + 15). Find the sum of first 20 terms of A.P.

the A.P. nth term of an A.P. is given by (-4n+15). Find the sum of first 20 terms of A.P.

If the nth term of an A.P. is t_(n) =3 -5n , then the sum of the first n terms is ………

Find the sum S_n of the cubes of the first n terms of an A.P. and show that the sum of first n terms of the A.P. is a factor of S_n .

In an A.P. given that the first term (a) = 54, the common difference (d) = -3 and the n^(th) term (a_(n))=0 , find n and the sum of first n terms (S_(n)) of the A.P.