Now let's try to find f of four and f of negative two. Alright, f of four, well, wherever we see the next, we substitute a four there, it's going to be integral from one to four of f prime of u du plus three. So what is going to be the integral from one to four of f prime of u du? So let's look up here. So the integral from one to four of f prime, that's that curve right over here. Well, that's going to give this area, but it's going to be the negative of the area because if you just take the integral, it's the area that you could view above the x-axis and below, or if we're thinking in terms of view, above the u-axis and below the function. But this is the other way around.