| source: knowledge_base | |
| topic: discrete_math | |
| class_level: class_11 | |
| difficulty: advanced | |
| Discrete Mathematics: | |
| Permutations: P(n,r)=n!/(n-r)!. Combinations: C(n,r)=n!/(r!*(n-r)!). | |
| GCD(a,b)=GCD(b,a mod b). LCM(a,b)=a*b/GCD(a,b). | |
| Modular: a≡b(mod n) means n divides (a-b). | |
| Fermat's Little: a^(p-1)≡1(mod p) for prime p. | |
| De Morgan: NOT(A AND B)=NOT(A) OR NOT(B). |