What does c mean?

The upper right corner of the mathematical symbol C is 1, and the lower right corner is 4, indicating the combination in mathematics. The lower right corner is 4, indicating the total number, and the upper right corner is 1, indicating the number of extractions. One of the four is extracted, and C=4÷ 1=4.

Combination: Generally speaking, taking m(m≤n) elements from n different elements as a group is called the combination of taking m elements from n different elements. The total number of all these combinations is called the combination number, and the calculation formula of this combination number is:

The combination obtained by repeatedly extracting M elements from N-ary set A is essentially an M-ary subset of A. ..

The properties of the combination number formed by taking out M different elements from N different elements at one time are as follows:

Using these two properties, we can simplify the calculation of combination number and prove the problems related to combination number.

C stands for combination.

C is 3 in the upper right corner and 5 in the lower right corner, that is to say, how many permutations and combinations of three things are selected from five things (in no particular order)?

Calculation method: 5! /3! *(5-3)! = 1*2*3*4*5/ 1*2*3* 1*2= 10

Along any two sides, greater than the third side.

That is, the combination of three numbers selected from five numbers is 10, minus the invalid (3,4,7)1;

Adding 5*4=20 isosceles triangle and subtracting 2 (3,3,6) (3,3,7) is invalid; There are five equilateral triangles; A * * * has 9+ 18+5=32.