In mathematics, numbers can be represented by points on a straight line, which is called the number axis and meets the following requirements:

(1) Take any point on a straight line to represent 0. This point is called the origin.

(2) Generally, from the origin to the right (or upward) is the positive direction, and from the origin to the left (or downward) is the negative direction;

(3) Choose an appropriate length as the unit length, and take a point every other unit length from the origin to the right on the straight line.

Extended data:

The role of the number axis:

1, the number axis can visually represent numbers, and the points on the horizontal number axis correspond to real numbers one by one, that is, each real number can be represented by a point on the number axis.

2. Compare the sizes of real numbers, with 0 as the center, and the number on the right is greater than the number on the left.

3. The imaginary number can also be represented by the vertical number axis perpendicular to the horizontal number axis and with the same origin, thus forming a complex plane with the horizontal number axis.

4. Two mutually perpendicular number axes with the same origin can form a plane rectangular coordinate system; Three mutually perpendicular number axes with the same origin can form a spatial rectangular coordinate system to determine the position of an object.

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