Well the average slope over this interval, or the average change, the slope of the secant line, is going to be our change in y, our change in y right over here, over our change in x, over our change in x. Well what is our change in y? Our change in y is f of b minus f of a, minus f of a, and that's going to be over, that is going to be over our change in x. Over b minus, b minus a. Let me do that in that right color. So let's just remind ourselves what's going on here. So this right over here, this is the graph of y is equal to f of x.