Answer
$(a-3)(a^2-2)$
Work Step by Step
Using factoring by grouping, the factored form of the given expression, $
a^3-3a^2+6-2a
,$ is
\begin{array}{l}
a^3-3a^2-2a+6
\\\\=
(a^3-3a^2)-(2a-6)
\\\\=
a^2(a-3)-2(a-3)
\\\\=
(a-3)(a^2-2)
.\end{array}