Answer: Choice C
Explanation:
If you graphed (x-6)(x+4) on the xy plane, then you'll see a parabola forming. This parabola has roots at x = -4 and x = 6. Between these roots, the curve is below the x axis. This visually shows that (x-6)(x+4) is negative when -4 < x < 6.
Furthermore, we can say that (x-6)(x+4) is negative or zero when [tex]-4 \le x \le 6[/tex] which corresponds directly to the number line graph your teacher gave you. The endpoints being closed circles mean "include this as part of the shaded solution set".