The formula of permutation and combination is A(n, m) = n× (n- 1). (n-m+ 1) = n/(n-m)。 Permutation and combination is the most basic concept of combinatorics. The so-called arrangement refers to taking out a specified number of elements from a given number of elements for sorting, while the combination refers to taking out only a specified number of elements from a given number of elements without considering the sorting.

Development of permutation and combination

The central problem of permutation and combination is to study the total number of possible situations in a given permutation and combination. Permutation and combination are closely related to classical probability theory. Although mathematics began in the ancient times of knot number, the development of social production level at that time was still in the low stage, and there was no skill.

With people's understanding and research on numbers, in the process of forming mathematical branches closely related to numbers, such as number theory, algebra, function theory and even functional, people gradually discover the diversity of numbers from the diversity of numbers, thus producing various counting techniques. At the same time, people have a profound understanding and research on numbers, and in the process, various mathematical branches closely related to shapes have been formed, such as geometry, topology and even category theory.