## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Multiplying both the numerator and denominator by $b ,$ the given expression, $\sqrt[]{\dfrac{a}{b^3}} ,$ is equivalent to \begin{array}{l}\require{cancel} \sqrt[]{\dfrac{a}{b^3}} \\\\= \sqrt[]{\dfrac{a}{b^3}\dfrac{b}{b}} \\\\= \sqrt[]{\dfrac{a\cdot b}{b^3\cdot b}} .\end{array} Hence, $\text{ Choice B .}$