So that's saying that given that the first derivative at x equals negative four is equal to zero, and you can see that the slope of the tangent line when x is equal to negative four does indeed equal zero. So given that, what is a calculus-based, let me underline that, a calculus-based justification for the fact that h has a relative maximum at x equals negative four? So this first one says that the second derivative at x equals negative four is negative. Now what does that tell us? If the second derivative is negative, that means that the first derivative is decreasing, which is another way of saying that we are dealing with a situation where, at least at x equals negative four, we are concave downwards, downwards, which means that the general shape of our curve is going to look something like this around x equals negative four. And if the slope at x equals negative four is zero, well, that tells us that, yes, we indeed are dealing with a relative maximum point. If the second derivative at that point was positive, then we would be concave upwards, and then if our derivative is zero there, we'd say, okay, that's a relative minimum point.