9a) $$f(x)=x^\frac{1}{3}$$
$$ \text{allgemein }f'(x)=n\cdot x^{n-1}\\f'(x)=\frac{1}{3}\cdot x^{\frac{1}{3}-1}\\ =\frac{1}{3}x^{-\frac{2}{3}}\\ =\frac{1}{3x^{\frac{2}{3}}}$$
b)
$$f(x) =\sqrt{x}=x^\frac{1}{2}\\ f'(x)=\frac{1}{2}x^{\frac{1}{2}-1}\\ =\frac{1}{2}x^{-\frac{1}{2}}\\ =\frac{1}{2\sqrt{x}}\\ \text{usw.}$$