If the equation is then the domain is the set of all real numbers.
We can replace x with any real number and compute to get some real number output for y. There are no division by zero restrictions to worry about, or issues with taking a square root of a negative number (since this isn't really a square root function).
The cube root of a negative number is negative. For example, because (-4)^3 = (-4)*(-4)*(-4) = -64.
In interval notation, the domain would be written as to indicate the entire real number line.