[7^(" th ")" term of an A.P.is "40," then the sum of first "13" terms "],[" is "]

7th term of an A.P. is 40. then the sum of the first 13 terms is

If the 7^(th) term of n A.P is 40. Then the sum of its first 13 terms is

If sum of 4^( th ) . 7^( th ) & 10^( th ) term of an A .P .is 15 ,then sum of first thirteen terms of same A.P.is

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

If n^(th) term of an A.P.is 2n+1. Find the sum of n term.

The 13^(th) term of an A.P is 3 and the sum of first 13 terms is 234 . Find the common difference and the sum of first 21 terms .

If 12 th term of an A.P.is -13 and the sum of the first four terms is 4, what is the sum of first 10 terms?

If the 10 th term of an A.P.is 21 and the sum of its first ten terms is 120, find its nth term.

In the sum of first n terms of an A.P.is cn^(2), then the sum of squares of these n terms is