## Calculus (3rd Edition)

a) $f(x) = x^2$ c) $f(x) = x ^\pi$ f) $f(x) = x^\frac{-4}{5}$
The power rule applies only when a variable is raised to a constant power. We rule b) $f(x) = 2\pi$ and d) $f(x) = \pi^x$ out because the value being raised is a constant. We rule e) $f(x) = x^x$ out because the variable is not being raised to a constant power.