Giải thích các bước giải:
$\begin{array}{l}
P = x + y + \frac{2}{x} + 2019\\
= \frac{x}{3} + y + \frac{{2x}}{3} + \frac{2}{x} + 2019\\
{\mathop{\rm co}\nolimits} :x + 3y \ge 9 \Rightarrow \frac{x}{3} + y \ge 3\\
va:theo\,Co - si:\frac{{2x}}{3} + \frac{2}{x} \ge 2\sqrt {\frac{{2x}}{3}.\frac{2}{x}} = \frac{4}{{\sqrt 3 }} = \frac{{4\sqrt 3 }}{3}\\
P \ge 3 + \frac{{4\sqrt 3 }}{3} + 2019 = 2022 + \frac{{4\sqrt 3 }}{3}\\
\min P = 2022 + \frac{{4\sqrt 3 }}{3}\\
dau = xay\,ra\, \Leftrightarrow x = \sqrt 3 ;y = 3 - \frac{{\sqrt 3 }}{3}
\end{array}$
