The definition of harmonious point in junior high school mathematics refers to the vertical lines that pass through a point respectively in the plane rectangular coordinate system and serve as the coordinate axis. If the perimeter and area of the rectangle enclosed by the coordinate axis are equal, this point is called a harmonic point. The coordinates of point P(x, y) satisfy x+y=xy, so P is called a harmonic point.

Introduce the concept of harmonious point into junior high school mathematics to cultivate students' geometric thinking and problem-solving ability.