Answer:
choose x ≥ 0 or x ≤ 0
Step-by-step explanation:
The vertex of the parabola is at x=0. If values of x are included from both sides of the vertex, the function will not pass the horizontal line test. So, the domain must be limited so that it does not include both positive and negative values of x.
The domain could be x ≥ 0, or x ≤ 0, or some subset of either of these intervals.
