Solve Fourth Root Division: Simplifying (Fourth Root of 128)/(Fourth Root of 8)

Introduction:

We will address the following two laws of exponents:

a. The definition of root as an exponent:

$\sqrt[n]{a}=a^{\frac{1}{n}}$

b. The law of exponents for an exponent applied to terms in parentheses:

$(\frac{a}{b})^n=\frac{a^n}{b^n}$

Note:

By combining these two laws of exponents mentioned in a (in the first and third steps below) and b (in the second step below), we can derive another new rule:

$\sqrt[n]{\frac{a}{b}}=\\ (\frac{a}{b})^{\frac{1}{n}}=\\ \frac{a^{\frac{1}{n}}}{ b^{\frac{1}{n}}}=\\ \frac{\sqrt[n]{a}}{ \sqrt[n]{ b}}\\ \downarrow\\ \boxed{ \sqrt[n]{\frac{a}{b}}=\frac{\sqrt[n]{a}}{ \sqrt[n]{ b}}}$

Therefore, in solving the problem, meaning - simplifying the given expression, we will use the new rule we received in the introduction:

$\boxed{ \sqrt[n]{\frac{a}{b}}=\frac{\sqrt[n]{a}}{ \sqrt[n]{ b}}}$

We'll start by simplifying the expression using the rule we received in the introduction (but in the opposite direction, meaning we'll insert the product of roots as a product of terms under the same root) then we'll perform the multiplication under the root and finally we'll perform the fifth root operation:

$\frac{\sqrt[4]{128}}{\sqrt[4]{8}}= \\ \sqrt[4]{\frac{128}{8}}=\\ \sqrt[4]{16}=\\ \boxed{2}$

Therefore, the correct answer is answer B.