\textbf{2.} Spo�t�te parci�ln� derivace 1. a 2. ��du funkce
    $u = x^4 + y^4 - 4x^2y^2$

    \textbf{�e�en�}
    \begin{align*}
        \frac{\partial u}{\partial x} &= 4x^3 - 8xy^2\\
        \frac{\partial u}{\partial y} &= 4y^3 - 8x^2y\\
        \frac{\partial^2 u}{\partial x \partial y} &=
        \frac{\partial^2 u}{\partial y \partial x} = -16xy\\
        \frac{\partial^2 u}{\partial x^2} &= 12x^2 - 8y^2\\
        \frac{\partial^2 u}{\partial y^2} &= 12y^2 - 8x^2
    \end{align*}
