$${ x }^{ 2 } \times { x }^{ 2 } = { \left(2 \sqrt{ 2a } \right) }^{ 2 }$$
$\left\{\begin{matrix}\\a=\frac{x^{4}}{8}\text{, }&\text{unconditionally}\\a=0\text{, }&x=0\end{matrix}\right.$
$\left\{\begin{matrix}x=-2^{\frac{3}{4}}\sqrt[4]{a}\text{; }x=2^{\frac{3}{4}}\sqrt[4]{a}\text{, }&a\geq 0\\x=0\text{, }&a=0\end{matrix}\right.$
