Well, to do that, let's just calculate what this has to be. Then let's just take the derivative and set them equal and we should be able to solve for our c. So let's see, f of 5 minus f of 2. f of 5 is equal to 25 minus 30 plus 8. So that's negative 5 plus 8 is equal to 3. f of 2 is equal to 2 squared minus 12. So it's 4 minus 12 plus 8, that's going to be 0. So this is equal to 3 over 3, which is equal to 1. f prime of c needs to be equal to 1. And so what is the derivative of this? Well, let's see, f prime of x is equal to 2x minus 6.