In the calculus slides, it is shown that the rule

$$\frac{d}{dx}{x}^n=n{x}^{n-1}$$

also works for fractional, negative, and even zero exponents. However, one function is still “missing” from the table of power derivatives. Which function is it?

a) $x^{-2}$
b) $x^{-1}$
c) $\ln x$
d) $e^x$
e) $\sqrt{x}$