We're told to consider the curve given by the equation, they give this equation. It can be shown that the derivative of y with respect to x is equal to this expression, and you could figure that out with just some implicit differentiation and then solving for the derivative of y with respect to x. We've done that in other videos. Write the equation of the horizontal line that is tangent to the curve and is above the x-axis. Pause this video and see if you can have a go at it. So let's just make sure we're visualizing this right. Let me just draw a quick and dirty diagram.