So let's think about the interval when we go from negative infinity to two. And let's think about the interval where we go from two to positive infinity. If you want, you could have some test values. 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.