Answer
$-20$
Work Step by Step
Given that $
a_n=-2n
$ then the first 4 terms are
\begin{array}{l}
a_1=-2(1)\\
a_1=-2
,\\\\
a_2=-2(2)\\
a_2=-4
,\\\\
a_3=-2(3)\\
a_3=-6
,\\\\
a_4=-2(4)\\
a_4=-8
.\end{array}
Hence, the sum is $
-2-4-6-8
=
-20
.$