Carcass wrote:
\(v, w, x, y, z\)
A geometric sequence is a sequence in which each term after the first is equal to the product of the preceding term and a constant. If the list of numbers shown above is an geometric sequence, which of the following must also be a geometric sequence?
I. \(2v, 2w, 2x, 2y, 2z\)
II. \(v + 2, w + 2, x + 2, y + 2, z + 2\)
III. √v,√w,√x,√y,√z
(A) I only
(B) II only
(C) III only
(D) I and II
(E) I and III
Let the numbers be 1, 3, 9, 27, 81 with \(r = 3\)
Check the option choices;
I. \(2, 6, 18, 54, 162\)
\(r = \frac{6}{2} = \frac{18}{6} = \frac{54}{18} = \frac{162}{54} = 3\)
II. \(3, 5, 11, 29, 83\)
Clearly not a G.PIII. \(√1, √3, √9, √27, √81\)
\(r = \frac{√3}{√1} = \frac{√9}{√3} = \frac{√27}{√9} = \frac{√81}{√27} = √3\)
Hence, option E