Where, let's go back to our graph and see when is f prime of x less than zero and decreasing. So if we look at less than zero, let me highlight this enough. So less than zero, I'm highlighting it in magenta right over here. This is all the places where we are less than zero in magenta. And now of that, where are we decreasing? Well we are decreasing over this interval, right over here. So that would be negative two is less than x, which is less than negative one.