## anonymous 5 years ago Which of the following are geometric sequences?Check all that apply. A. 2, -2, 2, -2, 2, -2, 2 B. 1, 2, 4, 8, 16, 32 C. 1, 4, 9, 16, 25, 36, 49 D. 10, 5, 2.5, 1.25, 0.625, 0.3125

1. anonymous

first one is $2\times (-1)^{n+1}$ go geometric. notice that each ratio is -1

2. anonymous

second one is $2^{n-1}$ also geometric. notice again that common ratio is 2

3. anonymous

third one is $n^2$ not geometric because for example $\frac{25}{16}\neq \frac{36}{25}$

4. anonymous

last one ... take the ratio of any two successive terms. if those ratios are the same, then it is geometric.