<span>Formula f(n+1) = 1.5 f(n) => f(n+1) / f(n) = 1.5.
That means, that you have to search for a sequence where the ratio of two consecutive terms is 1.5.
The first sequence is the only one that meets that:
- 18 / - 12 = 1.5 and
- 27 / - 18 = 1.5.
So, the answer is the first option: -12, -18, -27, ...</span>