Answer
It is a geometric sequence.
$r=-\frac{1}{2}$
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:
$\frac{a_2}{a_1}=\frac{-24}{48}=-\frac{1}{2}$
$\frac{a_3}{a_2}=\frac{12}{-24}=-\frac{1}{2}$
$\frac{a_4}{a_3}=\frac{-6}{12}=-\frac{1}{2}$
It is a geometric sequence.
Common ratio: $r=-\frac{1}{2}$
