On the number axis, the distance from a point representing a number to the origin is called the absolute value of the number, and the absolute value is represented by "||". On the number axis, assuming a>b, a>0, b>0, then the value of the distance from the point representing number a to the point representing number b is read as the absolute value of ab, and written as |ab|.

For example: |5| refers to the distance between the point representing the number 5 on the number axis and the origin. This distance is 5, so the absolute value of 5 is 5. Similarly, |-5| refers to the distance between the point representing the number -5 on the number axis and the origin. This distance is 5, so the absolute value of -5 is also 5.

The absolute value of a non-negative number (positive number and 0) is itself, and the absolute value of a non-positive number (negative number and 0) is its opposite.

The absolute value of a is represented by “|a|” and is read as “the absolute value of a”.

The absolute value of a real number a is always non-negative, that is, |a|≥0.

The absolute values ​​of two opposite numbers are equal, that is, |-a|=|a| (because their distances from the origin on the number axis are equal).

If a is a positive number, then x has two values ​​±a that satisfy |x|=a, such as |x|=3, then x=±3.