So the inverse of e to the x is natural log of x. And once again, that's all review of inverse functions. If that's unfamiliar, review it on Khan Academy. So g of x is going to be equal to the natural log of x. Now, let's see if this holds true for these two functions. Well, what is f prime of x going to be? Well, this is one of those amazing results in calculus, one of these neat things about the number e is that the derivative of e to the x is e to the x.