ANSWER:all real numbers less than or equal to 0.
Step-by-step explanation:
When you reflect a function across the x-axis, you negate every y-coordinate in the function.
In our original function, our y-values will all be positive. Reflecting this across the x-axis will make all of the y-values negative; this means the range, or set of y-values, will be less than or equal to 0.