The simplified forms of the radical expressions are:
- For \( \sqrt[3]{16 x^{5}} \): \( 2x \sqrt[3]{2 x^{2}} \)
- For \( \sqrt{45 x^{2} y^{-4}} \): \( \frac{3x \sqrt{5}}{y^2} \)
Thus, the final answers are:
\[
\boxed{2x \sqrt[3]{2 x^{2}}}
\]
\[
\boxed{\frac{3x \sqrt{5}}{y^2}}
\]