So this is true. A critical point is at x equals zero. But a question is, is this the only critical point? 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?