## Algebra and Trigonometry 10th Edition

A sequence is geometric if $\frac{a_2}{a_1}=\frac{a_3}{a_2}=\frac{a_4}{a_3}=...=r$ For the given sequence we have that: $\frac{a_2}{a_1}=\frac{10}{5}=2$ $\frac{a_3}{a_2}=\frac{15}{10}=1.5$ It is not a geometric sequence.