Let `a_n` be the `nth` term of an `A.P` and `a_3 +a_5 + a_8+a_14+a_17+a_19=198`.Find the sum of first 21 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.

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

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

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.

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.

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

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

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

If the sum of first term of an A.P is 49 and that of 17 terms is 289. Find the sum of first "n" terms. OR The sum of the third and seyenth terms of an AP is 6 and their product is 8. find the sum of first sixteen terms of the A.P.