" 1) If the sum of first "k" terms of "an A*P" is "(1)/(2)(3x^(2)+7x)" ,write its "k" them "1" lence "

If sum of first n terms of an A.P is 2n^(2) + 7n, write its nth term.

If the sum of the first n terms of an A.P.is (1)/(2)(3n^(2)+7n), then find its nth term.Hence write its 20 th term.

If the sum of the first n terms of an A.P. is 1/2(3n^2+7n) , then find its nth term. Hence write its 20th term.

If the sum of first k terms of an A.P.is 3k^(2)-k and its common difference is 6. What is the first term?

If the sum of first k terms of an A.P. is 3k^2-k and its common difference is 6. What is the first term ?

The difference between the sum of the first k terms of the series 1^(3)+2^(3)+3^(3)+...+n^(3) and the sum of the first k terms of 1+2+3+....+n is 1980. The value of k is :

The difference between the sum of the first k terms of the series 1^(3)+2^(3)+3^(3)+...+n^(3) and the sum of the first k terms of 1+2+3+...+n is 1980. The value of k is

If the sum of the first n terms of a sequence is 2(7^(n)-1)//3 show that it is a G.P. Also , find its first term and common ratio.

The difference between the sum of the first k terms of the series 1^3+2^3+3^3++n^3 and the sum of the first k terms of 1+2+3++ni s1980. The value of k is __________.

If the sum of sirst n terms of a G.P is p.sum of its first 2n terms is 3p,Prove that the sum of its first 3n terms is 7p.