The domain of a function is the set of all possible input values for which the function is defined.
In this case, the function is f(x) = x^2 sgn(x), where sgn(x) is the sign function. The sign function returns -1 if x is negative, 0 if x is zero, and 1 if x is positive.
Since x^2 is defined for all real numbers, the only restriction on the domain comes from the sign function. The sign function is defined for all real numbers except for x = 0, where it is undefined.
Therefore, the domain of f(x) = x^2 sgn(x) is all real numbers except for x = 0. In interval notation, the domain can be written as (-∞, 0) U (0, ∞).