\[\boxed{\mathbf{501}.}\]
\[1)\ \frac{a - b}{\sqrt[3]{a} - \sqrt[3]{b}} - \frac{a + b}{a^{\frac{1}{3}} + b^{\frac{1}{3}}} =\]
\[= \frac{a^{\frac{1}{3}} - b^{\frac{1}{3}}}{a + b} - \frac{a^{\frac{1}{3}} + b^{\frac{1}{3}}}{a + b} =\]
\[= \frac{- 2b^{\frac{1}{3}}}{a + b} = - \frac{2\sqrt[3]{b}}{a + b}.\]