## Calculus with Applications (10th Edition)

$(-\infty,\infty)$
We are given that $f(x)=x^4$ and want to determine all possible real numbers $x$ such that $x^4$ is defined. We can always raise any real number to the fourth power, so the domain of $f$ is all real numbers, which can be expressed in interval notation as $(-\infty,\infty)$.