Y minus y one over x minus x one is equal to b. Because this comes straight out of the idea of, look, if x one and y one are on the line, the slope between any other point on the line and that point is going to be your slope of your line. So we could think about it any of these ways. So let's first find the slope of the tangent line, and that's where the derivative is useful. So f, well, actually, let me just write f of x again. So I'm gonna write it as x minus one to the negative one power, because that makes it a little bit clearer that we can use the power rule and a little bit of the chain rule. So the derivative of f with respect to x is equal to, so the derivative of x minus one to the negative one with respect to x minus one, well, that's just going to be, we're just going to use the power rule here.