Interval:
Interval, a concept in the field of mathematics, is very common in middle school mathematics and refers to a continuous interval. Any continuous block allocated to an object (such as a table) is called an interval; An interval is also called an extension because when it runs out of allocated intervals, a new record needs to be inserted.
Interval must be assigned a new interval (that is, extend some blocks); Once an interval is assigned to one object (table, index and cluster), it cannot be assigned to other objects. It is divided into closed interval, open interval and semi-open and semi-closed interval. Mathematical interval refers to a certain range. There are fully open intervals, fully closed intervals, semi-open and semi-closed intervals and semi-closed and semi-open intervals.
Full-open interval: the symbol is (), which refers to an interval without endpoints, such as (2,4), which means a real number within the range of real numbers greater than 2 and less than 4;
Fully closed interval: the symbol is [], which refers to the interval containing endpoints, such as [2,4], which means real numbers within the real number range of 2 and 4;
Semi-open and semi-closed interval: the symbol is [], which refers to the interval that does not contain the minimum data endpoint, but contains the maximum data endpoint, for example, [2,4], which indicates the real number within the real number range greater than 2 and less than or equal to 4;
Semi-closed and semi-open interval: the symbol is [], which refers to the interval that contains the minimum data endpoint, but does not contain the maximum data endpoint, such as [2,4], which indicates the real number within the real number range greater than or equal to 2 and less than 4.
When studying functions, the concept of interval is often used, and interval is a common predicate and symbol in mathematics. Let a, bR and a meet the inequality axb, and the set of real numbers X is called a closed interval, which is expressed as [a, b]; Satisfy inequality A. Here, real numbers A and B satisfying inequality ax are called the endpoints of the corresponding interval. On the number axis, these intervals can be represented by line segments with endpoints A and B. In the figure, the endpoints included in the interval are represented by solid lines, and the endpoints not included in the interval are represented by hollow points.