## Elementary Algebra

The domain of this function is $\{x|ℝ \;\text{(All real numbers)}\}$.
When this question asks for the domain of the function, it is asking for the values of $x$ that can be legally substituted into the function. (For instance, in the function $\frac{1}{x}$, $x\ne0$ because this would make the denominator of the fraction equal to 0, making the function at that value be undefined.) In the case of the function $y=-2x^4$, there are no values of $x$ that would make the function undefined. Therefore, the domain of this function is $\text{All real numbers}$.