Question

If the sequence is geometric, what is its common ratio?
-1, -6, -36, -216, …
Question 3 answers

-6

6

-5

not geometric

Answer 1

6 since
(-1) x 6 = -6
(-6) x 6 = -36
(-36) x 6 = -216.

To test if the sequence is geometric, find the ratio of a term to the preceding term. We must calculate at least several pairs or all the given pairs. The tricky of this question is that all terms are negative. This could confuse some students and lead to the thought that r = -6.