the sum of first n terms of `1+3+7+15+31+….`

If the sum of first n terms of a G.P is p and the sum of the first 2n terms is 3p,show that the sum of first 3n terms is7p.

If the sum of first n terms of two A.P's are in the ratio 3n+8: 7n+15 ,then the ratio of 12th term is

If the sum of the first n terms of a G.P. = p and the sum of the first 2n terms = 3p, show that the sum of first 3n terms = 7p.

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.

Let S_k denotes sum of first k terms of sequence 3,7,11, 15-----------Value of n, if 40lt6/(n(n+1))sum_(k=1)^nS_klt42 is________

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