Chapter 5 - Polynomials and Factoring - 5.1 Introduction to Factoring - 5.1 Exercise Set - Page 311: 67

$\dfrac{y^{4}}{2x}$

The given expression, $ (2xy^{-4})^{-1} ,$ simplifies to \begin{array}{l}\require{cancel} 2^{-1}x^{-1}y^{-4(-1)} \\\\= 2^{-1}x^{-1}y^{4} \\\\= \dfrac{y^{4}}{2^{1}x^{1}} \\\\= \dfrac{y^{4}}{2x} .\end{array}