This right over here is definitely a critical number. Now have we found all of the critical numbers? Well, this is the only number other than negative 2, the only number in the interval that will make f prime of x equal to zero. What about where it's undefined? Well, f prime of x would be undefined. The only place it would be undefined is if you stuck a zero right over here in the denominator, but zero is not in the interval. So the only critical number in the interval is x equals 2.