And then it's going to be that number squared. So it's going to be 3 plus delta x squared. What is that? That's going to be 9. I'm just FOILing this out, or you do the distributive property twice. If a plus b squared is a squared plus 2ab plus b squared, so it's going to be 9 plus 2 times the product of these things. So plus 6 delta x, and then plus delta x squared.