Đáp án:
$\begin{array}{l}
A = \frac{{8{x^2} + 2}}{x} = 8x + \frac{2}{x}\\
Theo\,Co - si:8x + \frac{2}{x} \ge 2.\sqrt {8x.\frac{2}{x}} = 2.\sqrt {16} = 8\\
\Rightarrow GTNN:A = 8\\
\Leftrightarrow 8x = \frac{2}{x} \Rightarrow x = \frac{1}{2}\left( {do:x > 0} \right)
\end{array}$