If the `n^(t h)` term of an A.P., is `(2n+1),` then the sum of its first three terms is (a) 6n+3 (b) 15 (c) 12 (d) 21

If the n^(th) term of an A.P.is (2n+1), then the sum of its first three terms is (a) 6n+3 (b) 15 (c) 12 (d) 21

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

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

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

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 10 t h term of an A.P. is 21 and the sum of its first ten terms is 120, find its n t h term.

The nth term of an A.P. is p, show that, the sum of its first (2n-1) terms is (2n-1)p.