The nth term of an A.P. is (5n-1). Find the sum of its 'n' terms.

The nth term of an A.P. is 7n-5, find the sum of first 20 terms of the series.

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.

The nth term of an A.P. is p and the sum of its first n terms is q. Prove that its first term is (1)/(n)(2q-p n) .

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

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 sum of n terms of an A.P. is 3n^(2) + 5n . Find the number of the term which is equal to 152.

The nth term of a series in A.P. is an + b. Find the sum of the series up to n terms.

Find the sum of first n terms of an AP whose nth term is (5n-1). Hence,find the sum of first 20 terms.