Now I haven't changed the value, I just added and subtracted the same thing. But now this thing can be manipulated in interesting algebraic ways to get us to what we all love about the product rule. And at any point you get inspired, I encourage you to pause this video. Well, to keep going, let's just keep exploring this expression. So all of this is going to be equal to, it's all going to be equal to the limit as h approaches zero. So the first thing I'm going to do is I'm going to look at this part, this part of the expression. And in particular, let's see, I am going to factor out an f of x plus h. So if you factor out an f of x plus h, this part right over here is going to be f of x plus h, f of x plus h, times, you're going to be left with g of x plus h, g of, it's a slightly shader, different shade of green, g of x plus h, that's that there, minus g of x, minus g of x, whoops, I forgot the parentheses.