Did I, let's see, that's a long word, differentiability. All right, differentiability, what needs to be true here? Well we have to have a defined limit as x approaches one for f of x minus f of one over, oh let me be careful, it's not f, it's g. So we need to have a defined limit for g of x minus g of one over x minus one. And so let's just try to evaluate this limit from the left and right-hand sides. And we could simplify it, we already know that g of one is zero, so that's just going to be zero. So we just need to find the limit as x approaches one of g of x over x minus one, or see if we can find a limit. So let's first think about the limit as we approach from the left-hand side of g of x over x minus, g of x over x minus one.