[" 15) If the "m^(" th ")" term of an "AP" is "(2n+1)" then "],[" find the sums of first three iterm "]

If n^(th) 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 n^(th) term of an AP be (2n-1) then the sum of its first n terms will be

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

If the sum of n terms of an AP is n^2-2n then find its n^(th) term

If the n^(th) term of an A.P is 2n-1 then sum to n terms of that A.P. is ........... .

If the m^th terms of an AP is 1/n and the n^th term is 1/m , prove that the sum of the first mn terms is 1/2(mn+1)

Find the sum of first n terms of an AP whose n^(th) term is 5-6n .find the sum of its first 20 terms

If the sum of first n terms of an A.P. is 3n^(2)-2n , then its 19th term is