In this case, the something is y, so two times y, and then times the derivative of y, the derivative of y with respect to x. And this is all going to be equal to, all going to be equal to zero. Now that was interesting. Now we have an equation that has the derivative of y with respect to x in it. And this is what we essentially want to solve for. This is the slope of the tangent line at any point. So all we have to do at this point is solve for the derivative of y with respect to x, solve this equation.