Well, as we've mentioned, a critical point is where a function's derivative is either equal to zero or it's undefined. This is the only one where the derivative is equal to zero. But can you find some x values where the derivative is undefined? Well, what if we make the derivative, what would make the denominator of the derivative equal to zero? Well, if x squared minus one is equal to zero, you take the cube root of zero, you're gonna get zero in the denominator. So what would make x squared minus one equal to zero? Well, x is equal to plus or minus one.