Alright, now for f to be decreasing, f is going to be decreasing if and only if, well you're decreasing when you have a negative slope, if your rate of change is negative. So that's true if and only if f prime of x is less than zero. So both true, both true when f prime of x is less than zero and decreasing. And let me write, and f prime is decreasing. And f prime decreasing. So let's see if we can identify that. Where, let's go back to our graph and see when is f prime of x less than zero and decreasing.