Simple...
you have: [tex]F= \sqrt[a]{ \frac{ 16a^{2} + 8a^{2} }{ 4a^{2}+ 2a^{2} } } [/tex]
As far as I can see this is pretty simple....
Simply divide it-->>>>
the [tex] a^{2} [/tex] cancel out-->>
[tex]F= \sqrt[a]{ \frac{24}{6} } [/tex]
[tex]F= \sqrt[a]{4} [/tex]
Thus, your answer.