Chapter 6 Rational Exponents and Radical Functions - 6.2 Apply Properties of Rational Exponents - 6.2 Exercises - Skill Practice - Page 424: 38

$$-16\sqrt[4]{2}$$

In order to solve this problem, we may need to use the rules of radicals, which are listed on page 421. Once we have done this, we combine like radicals. Doing this, we find that the expression simplifies to: $$12\sqrt[4]{2}-28\sqrt[4]{2} \\ -16\sqrt[4]{2}$$