Chapter 7 - Exponents and Exponential Functions - 7-8 Geometric Sequences - Practice and Problem-Solving Exercises - Page 470: 21

Geometric, the common ratio is -3.

You have the sequence:2, -6, 18, -54. Find the common ratio by using the formula: R=$\frac{a2}{a1}$,R=$\frac{a4}{a3}$. Plug in the values to get the ratios. r=$\frac{-6}{2}$=-3 r=$\frac{-54}{18}$=-3 There is a common ratio, r=-3. So the sequence is geometric.