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

Find the sum of 20 terms of the A.P.1,4,7,10..

If the nth term of an A.P. is 4n-1 , find the 30th term and the sum of first 30 terms.

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

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

The sum of the third and the seventh terms of an A.P. is 6 and the product is 8. Find the sum of first sixteen terms of the A.P

Find the sum of the first 10 terms of the A.P. 6,4,2,…..

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

The sum oif the first ten terms of an A.P. is equal to 155, and the sum of the first two terms of a G.P. is 9. Find these progressionsif the first term of the A.P. equals the common ratio of the G.P. and the 1st term of G.P. equals the common difference of A.P.

If the sum of first 7 terms of an A.P. is 49 and that of its 17 terms is 289, find the sum of first n terms of the A.P.

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.