\[\begin{array}{l} {\text{Упростите:}} \hfill \\ {\left( {\frac{1}{{\sqrt[4]{5} + \sqrt[4]{3}}}} \right)^4} + {\left( {\frac{1}{{\sqrt[4]{5} - \sqrt[4]{3}}}} \right)^4}. \hfill \\ \end{array}\]