It's really interesting to do college entrance examination questions after graduation. Hehe, it may not be professional for several years. You are correcting, and the overall meaning should be correct.

This problem is actually to take the points in the first quadrant on a straight line and make the vertical lines of the two coordinate axes. The vertical line and the coordinate axis will form a rectangle. Find the maximum area of the rectangle. Of course, you can also do it purely in algebraic form without drawing, as in the picture.