You give any x value over this interval, we have a value for f of x. f of x isn't differentiable everywhere, but definitely f of x is defined everywhere over the interval. So you'll get a number here, and obviously 2 is just 2, and you add 2 to it and you get the derivative of g at that point of the interval. So g is actually differentiable throughout the interval. So the only critical points would be where this derivative is equal to 0. So let's set this thing equal to 0. So we want to solve the equation, I'll just rewrite it actually. So we want to solve the equation g prime of x is equal to 0, or 2 plus f of x is equal to 0.