Question

Which of the following sequeces in GP will have common ratio 3, where n is an Integer?

(a) gn = 2n^2 + 3n

(b) gn = 2n^2 + 3

(c) gn = 3n^2 + 3n

(d) gn = 6(3^n-1)

I had been asked this question in an online quiz.

This interesting question is from Geometric Sequences in portion Basic Structures: Sets, Functions, Sequences, Sums and Matrices of Discrete Mathematics

Answer 1

The correct choice is (d) gn = 6(3^n-1)

For explanation I would say: gn = 6( 3^n-1) it is a geometric expression with coefficient of constant as 3^n-1.So it is GP with common ratio 3.