Rational exponents work like this:
[tex]a^{\frac{b}{c}}=\sqrt[c]{a^b}[/tex]
So, the numerator works as a usual power, while the denominator represents the order of the root.
So, raising to the power 1/4 means to extract the fourth root of a number:
[tex]64^{\frac{1}{4}}=\sqrt[4]{64}=4[/tex]
