And we have videos on critical points or critical values. And why those are relevant is those are the places, those are the possible places where the sign could change, the sign of g prime could change. So when is g prime of x equal to zero? Well the way to get g prime of x equal to zero is getting the numerator equal to zero and that's only going to happen if x squared is equal to zero or if x is equal to zero. So that's the only place where g prime of x is equal to zero. And where is g prime of x undefined? Well it's going to be undefined if the denominator becomes undefined.