It's not going to say, oh, this is your f of x. It's going to give you the value of the slope of the curve at that point. So f of x, if you put it into that function, it should tell you, oh, the slope at that point is equal to, if you put 3 there, you'll say, oh, the slope there is equal to 6. We saw that in the last example. So that's what we want to do. And we saw in the last, I think it was two videos ago, that we defined f prime of x to be equal to just the, well, I'll write it this way. It's the slope of the secant line between x and some point that's a little bit further away from x.