Với \(y\le0\Rightarrow A\le0\)
Với \(y>0\):
\(A=108.\frac{x}{2}.\frac{x}{2}.\frac{y}{3}.\frac{y}{3}.\frac{y}{3}\le\frac{108}{5^5}\left(\frac{x}{2}+\frac{x}{2}+\frac{y}{3}+\frac{y}{3}+\frac{y}{3}\right)^5=\frac{108}{5^5}\)
\(A_{max}=\frac{108}{5^5}\) khi \(\hept{\begin{cases}x=\frac{2}{5}\\y=\frac{3}{5}\end{cases}}\)