Which of the following statements are correct?

$($Select all that apply.$)$

$x^{\frac{a}{b}}=(x^a{)}^{\frac{1}{b}}$

$\frac{x^a}{x^b}=\frac{1}{x^{b-a}}$

$(x^a{)}^b=b{x}^a$

$(xa{)}^b=(xb{)}^a$

None of the Above