Đáp án:
$\begin{array}{l}
A = - 16a - \sqrt {\dfrac{9}{{25}}{a^2}} = - 16a - \dfrac{3}{5}\left| a \right|\\
+ Khi:a \ge 0\\
\Rightarrow \left| a \right| = a\\
\Rightarrow A = - 16a - \dfrac{3}{5}a = \dfrac{{ - 83}}{5}a\\
+ Khi:a < 0\\
\Rightarrow \left| a \right| = - a\\
\Rightarrow A = - 16a + \dfrac{3}{5}a = \dfrac{{ - 77}}{5}a
\end{array}$