1, the distance between two points on the axis.

It can be expressed in absolute value, that is, the absolute value of the difference between two points. For example, if the numbers represented by points A and B on the number axis are A and B, then AB=|a-b| or | B-A |.

2. A moving point on the number axis is represented by a letter.

It can be solved by addition or subtraction of rational numbers, that is, adding or subtracting the distance of the moving point from the number indicated by the starting point, adding in the positive direction and subtracting in the negative direction. For example, the number corresponding to point A on the number axis is-1, and point P starts from point A and moves to the right at a speed of 2 unit lengths per second. Let the movement time be t, then the number represented by point P is-1+2t.

3. The midpoint of the line segment between any two points on the number axis.

The sum of the numbers represented by two points is divided by two. If the points on the number axis represent numbers A and B, then the number represented by the midpoint of the line segment AB is (a+b)/2.