C of binomial distribution means combination, which is the combination number in high school mathematics. Choose three from five different numbers, and the algorithm is:

C(5，3)=5！ /[3! ×(5-3)! ]

5! =5×4×3×2× 1= 120

3! ×(5-3)! =3! ×2! =(3×2× 1)×(2× 1)= 12

C(5，3)= 10

Coefficient attribute:

1, and the equidistance coefficient between the first and second ends is equal.

2. When the binomial index n is odd, the middle two terms are the largest and equal.

3. When the binomial index n is even, the middle term is the largest.

4. The sum of odd and even terms in binomial expansion is the same, both of which are 2 (n- 1).

5. The sum of all the coefficients in binomial expansion is 2 n. ..