\[\begin{array}{l}
{\text{Докажите тождество:}} \hfill \\
\sqrt[8]{{\frac{{3 + 2\sqrt[4]{2}}}{{3 - 2\sqrt[4]{2}}}}} = \frac{1}{{14}}\left( {\sqrt {98 + 14\sqrt {35 + 21\sqrt 2 } } + \sqrt { - 98 + 14\sqrt {35 + 21\sqrt 2 } } } \right). \hfill \\
\end{array}\]