number axis
In mathematics, numbers can be represented by points on a straight line, which is called a number line.
The number axis 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 on the straight line from the origin to the right, indicating 1 (1 unit length to the right), 2 (2 unit lengths to the right), 3 (3 unit lengths to the right), …; From the origin to the left,-1 (left 1 unit length), -2 (2 unit lengths to the left) and -3 (3 unit lengths to the left) are expressed in a similar way.
On the number axis, besides the number 0, you need to represent any rational number that is not 0. According to the sign of this number, determine which side of the number axis it is on (usually positive numbers are on the right side of the origin and negative numbers are on the left side of the origin), then determine that it is several unit lengths away from the origin in the corresponding direction, and then draw the corresponding point.