Answer
$\dfrac{1}{6}a^6$
Work Step by Step
Multiplying the constants and multiplying the variables, the given expression, $
\left( -\dfrac{1}{3}a^4 \right)\left( -\dfrac{1}{2}a^2 \right)
,$ simplifies to
\begin{array}{l}\require{cancel}
\left( -\dfrac{1}{3} \right)\left( -\dfrac{1}{2} \right)a^{4+2}
\\\\=
\dfrac{1}{6}a^6
.\end{array}