Answer
$\{16, 7,-2,...\}$ is an arithmetic sequence with common difference $d=-9
$
Work Step by Step
In the given sequence, $\{
16,7,-2,...
\},$ the differences of a term and its previous term are
\begin{align*}\require{cancel}
a_2-a_1&=
7-16
\\&=
-9
,\\\\
a_3-a_2&=
-2-7
\\&=
-9
.\end{align*}
Since the differences of a term and its previous term are the same, then $
\{16, 7,-2,...\}$ is an arithmetic sequence with common difference $d=-9
.$
