Unrepeatable C (6,4 4) c (6 6,5)1,2,3 ............................................................................................................................................. . . In the number of N, N, take M combinations (repeatable) n m Q: c(n, m), what is the pronunciation? How to take four digits from 1-6 and bring them in? Can you teach me? 50 points. Thank you very much. A: This is the combination number. Take the combination number of m elements from n elements, such as c (6,4) = (6 * 5 * 4 * 3)/(1* 2 * 3 * 4) c (n, m) = [n * (n-1) * .. * (. M) = [n * (n-1) * ... * (n-m+1)] /( 1 * 2 * ... * m) followed by/(1* 2 * ... How is this required? Answer: Your question is not very clear. If you say it constitutes a number, you don't need to divide it by the following. If you just take it out, you don't need to form a number. Supplement: Only one combination is correct. Supplement: unrepeatable 15 group repeatable 6 4 = 1296 group supplement: estimation. Your question is whether the unrepeatable component of a number is 6*5*4*3=360 repeatable components or 1296 supplements: you didn't say whether you need to take four digits to form a four-digit number? If there is, it is 360 kinds, if not, it is 15 kinds of supplement: this is your own topic. The original question would never say such a thing. Supplement: for example, permutation and combination, if you don't learn these, you won't understand. If you take two numbers from 1, 2, 3, there are three ways to take them {1, 2} and {1, 3}. 3} If you say that two digits make up two digits, there are six kinds:12,21,13,31,23,32. Look at the formula and ask: If six digits make up four digits, there are 360 kinds. Where did 15 come from? Answer: I am dizzy. I have made it very clear. Examples are listed. 15 kinds are not arranged. 360 should be arranged to form a four-digit supplement: if you teach yourself to arrange and combine, make the definition clear first. In addition, the topic you asked is too ambiguous. I have been asking you if you want to form the difference between the four-digit 360 and 15. That's the problem: I finally understand, under your careful guidance, I finally understand, in fact, I don't know anything about these, I haven't studied at all! Thank you for your highest reward!