Answer
$|x^3|$
Work Step by Step
RECALL:
$\sqrt[n]{a^m} = a^{\frac{m}{n}}.$
Use the rule above to obtain
$x^{\frac{12}{4}}
\\=x^{3}.$
Note, however, that $x$ can be any real number.
This means that when $x$ is negative, $x^3$ is also negative.
Since the principal fourth root of an expression is nonegative, the answer above must be adjusted to $|x^3|.$
Thus,
$\sqrt[4]{x^{12}} = |x^3|.$
