What is the maximum value of the function $f(x)=\frac{18}{x^{2}-9}$ over the interval $-3< x< 3$ ?
a) 2
b) -2
c) $\infty$
d) 0

Step 1 ：The function $f(x)=\frac{18}{x^{2}-9}$ is undefined at $x=\pm3$. Therefore, we need to find the limit of the function as $x$ approaches $3$ and $-3$ from the left and right. If the limit is finite, then that is the maximum value. If the limit is infinite, then the function does not have a maximum value in the given interval.

Step 2 ：The limit of the function as $x$ approaches $3$ and $-3$ from the left and right is $-\infty$. Therefore, the function does not have a maximum value in the given interval.

Step 3 ：Final Answer: The maximum value of the function $f(x)=\frac{18}{x^{2}-9}$ over the interval $-3