Chapter 6 Rational Exponents and Radical Functions - 6.3 Perform Function Operations and Composition - Guided Practice for Examples 1, 2, and 3 - Page 429: 2

$$-9x^{\frac{2}{3}}$$

Given that the two expressions, $f(x)$ and $g(x)$ are functions, we know that they will follow the rules of functions listed on page 429. Knowing this, we obtain: $$(-2-7)x^{\frac{2}{3}}=-9x^{\frac{2}{3}}$$