Answer
It is not a geometric sequence.
Work Step by Step
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.
