Answer
$$\frac{-2x-7}{\left(x+2\right)\left(x-3\right)\left(x+3\right)}$$
Work Step by Step
We know the following:
$$ (f-g)(x)=f(x)-g(x)$$
Thus, we find:
$$ \frac{x-1}{x^2-x-6}-\frac{x+2}{x^2-9} \\ \frac{-2x-7}{\left(x+2\right)\left(x-3\right)\left(x+3\right)}$$