The function is $f(x) = \dfrac{(-1)(x + 2)}{x + 2}$.

This function is undefined when the denominator equals zero:

$x + 2 = 0$

$x = -2$

For all $x \neq -2$, the $(x + 2)$ factors cancel, giving $f(x) = -1$. But at $x = -2$, the function is undefined.

The value of $x$ at which $f(x)$ is undefined is $x = -2$.