Think of your derivative properties, especially the derivative of logarithmic functions, especially logarithmic functions, in this case, with base 10. If someone just writes log without the base, you can just assume that that is a 10 right over there. So pause the video and see if you can work through it. All right, so the key here is to remember that if I have f of x, let me do it over here, I'll do it over here, f of x, and I want to find f prime of, let's say f prime of some number, let's say a, this is going to be equal to the limit as x, or sorry, as h approaches zero is one way of thinking about it, as h approaches zero of f of a plus h minus f of a, all of that over h. So this looks pretty close to that limit definition, except we have these fives here. But lucky for us, we can factor out those fives, and we could factor them out out front here, but if you just have a scalar times the expression, we know from our limit properties that we can actually take those out of the limit themselves. So let's do that. Let's take both of these fives and factor them out.