And you could use different types of notation here, you could say, instead of writing this with the derivative operator, you could say this is the same thing as g prime of x, and likewise, you could say, well, that is the same thing as f prime of x. And so now we just want to evaluate this thing, and you might say, well, how do I evaluate this thing? Well, let's just try it. Let's just say, well, we want to evaluate f prime when x is equal to negative one. So we can write f prime of negative one is equal to, well, everywhere we see an x, let's put a negative one here. It's going to be f prime of negative one, f prime, lowercase f prime, it's a little confusing, lowercase f prime of negative one times g of negative one, g of negative one, minus f of negative one, f of negative one, times g prime of negative one, g prime of negative one, all of that over, let me do it in that same color, so I take my colors seriously. All right, all of that over, g of negative one squared, g of negative one squared.