Answer
Discontinuous at $ x=-3$
Work Step by Step
Recall that if $ f $ is a polynomial function, then we have $\lim_\limits{x\to a}f(x)=f(a)$.
$ f(x)=\dfrac{x^2-9}{x+3}$
Set $ x=-3$
$ f(-3)=\dfrac{(-3)^2-9}{-3+3}=0$
So, $ f(-3)$ is not defined.
Therefore, the function is discontinuous at $ x=-3$
