You could think about the sign, sign of our second derivative. And then based on that, you could think about concavity. Concavity of f. So let's think about what's happening. So you could take a test value, let's say one is in this interval, and let's say three is in this interval. And you could say one minus two squared is going to be, let's see, that's negative one squared, which is one. And then you're just going to, this is just going to be 12. So this is going to be positive.