Chapter 6 Rational Exponents and Radical Functions - 6.4 Use Inverse Functions - 6.4 Exercises - Quiz for Lessons 6.3-6.4 - Page 445: 18

$$y=\sqrt[4]{\frac{x+49}{9}},\:y=-\sqrt[4]{\frac{x+49}{9}}$$

Switching the elements of the domain and the range (in other words, the dependent and independent variables), we find that the inverse is: $$x=9y^4-49 \\ y=\sqrt[4]{\frac{x+49}{9}},\:y=-\sqrt[4]{\frac{x+49}{9}}$$