Answer
The sketch of the graph is as shown.
Work Step by Step
At $y=0$:
$$0=x^2-9$$ $$x^2=9$$ $$x=\pm\sqrt{9}=\pm 3$$ $$x=-3,3$$
Thus, two points are at $(-3,0)$ and $(3,0)$.
At $x=0$:
$$y=0^2-9$$ $$y=-9$$
Thus, another point is at $(0,-9)$.
Plotting the three points and drawing a curve passing them, the sketch of the graph is as shown.
