And we can do it at a bunch of values, so let's think about it. Let's think about when, we're at this point right over here, when x is two and y is two. When x is two and y is two, the derivative of y with respect to x is going to be two minus two. It's going to be equal to zero. And just with that, let's see, here, this slope on this slope field does not look like it's zero. This looks like it's negative one. So already I could rule this one out.