In order to find the extrema, we need to solve the equation
$$\frac{d}{d x} f{\left(x \right)} = 0$$
(the derivative equals zero),
and the roots of this equation are the extrema of this function:
$$\frac{d}{d x} f{\left(x \right)} = $$
the first derivative$$2^{\frac{x}{9 - x^{2}}} \left(\frac{2 x^{2}}{\left(9 - x^{2}\right)^{2}} + \frac{1}{9 - x^{2}}\right) \log{\left(2 \right)} = 0$$
Solve this equationSolutions are not found,
function may have no extrema