\[\boxed{\mathbf{54}\mathbf{.}}\]
\[1)\ \frac{\sqrt{a} - \sqrt{b}}{\sqrt[4]{a} - \sqrt[4]{b}} - \frac{\sqrt{a} + \sqrt[4]{\text{ab}}}{\sqrt[4]{a} + \sqrt[4]{b}} =\]
\[= \sqrt[4]{a} + \sqrt[4]{b} - \sqrt[4]{a} = \sqrt[4]{b}\]
\[2)\ \frac{a - b}{\sqrt[3]{a} - \sqrt[3]{b}} - \frac{a + b}{\sqrt[3]{a} + \sqrt[3]{b}} =\]
\[= \frac{\sqrt[3]{a^{2}} - \sqrt[3]{\text{ab}} + \sqrt[3]{b^{2}} - \sqrt[3]{\text{ab}}}{\left( \sqrt[3]{a} - \sqrt[3]{b} \right)^{2}} =\]
\[= \frac{\sqrt[3]{a^{2}} - 2\sqrt[3]{\text{ab}} + \sqrt[3]{b^{2}}}{\sqrt[3]{a^{2}} - 2\sqrt[3]{\text{ab}} + \sqrt[3]{b^{2}}} = 1\]