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. Now, can we figure out what f prime of negative one, f of negative one, g of negative one, and g prime of negative one, what they are? Well, some of them they tell us outright. They tell us f and f prime at negative one, and for g, we can actually solve for those.