\(\Leftrightarrow\frac{x^2}{\sqrt{16-x^2}}=16-x^2\Leftrightarrow x^2=\sqrt{\left(16-x^2\right)^3}\)
Đặt \(t=\sqrt{16-x^2};\text{ }0\le t\le4\Rightarrow x^2=16-t^2\)
\(\Rightarrow16-t^2=t^3\Leftrightarrow t^3+t^2-16=0\)
\(\Leftrightarrow t=\frac{1}{3}\left(-1+\sqrt[3]{215-12\sqrt{321}}+\sqrt[3]{215+12\sqrt{321}}\right)\)