5.
[tex]a = 0,5^{-2,25} = (\frac{1}{2})^{-\frac{225}{100}} = (\frac{1}{2})^{-\frac{9}{4}}=2^{\frac{9}{4}}\\\\\\b=\sqrt[3]{\sqrt[4]{8}}} = (8^{\frac{1}{4}})^{\frac{1}{3}} =( (2^{3})^{\frac{1}{4}})^{\frac{1}{3}} = 2^{3\cdot\frac{1}{4}\cdot\frac{1}{3}} = 2^{\frac{1}{4}}\\\\\\\frac{a}{b} = \frac{2^{\frac{9}{4}}}{2^{\frac{1}{4}}}=2^{\frac{9}{4}-\frac{1}{4}} = 2^{\frac{8}{4}} = 2^{2} = 4\\\\\frac{a}{b} = 4\\\\\underline{a = 4b}\\\\c.n.u.[/tex]