Question

Exemple de combinari rezolvate

Answer 1

C₄¹ ( combinari de 4 luate cate 1) = $[tex] \frac{n!}{k!(n-k)!}$ = $\frac{4!}{1!(4-1)!}$ = $\frac{4!}{1!3!}$ = $\frac{3!4}{3!1}$$\frac{4}{1}$ = 1

Nota= 1!=1; 2!=1·2; 3!=1·2·3; 4!=1·2·3·4; 5=1·2·3·4·5; etc 
C₃² + C₇⁵ (Combinari de 3 elem. luate cate 2 + combinari de 7 elem. luate cate 5) =$\frac{3!}{2!1!} + \frac{7!}{5!2!}$ = $\frac{2!3}{2!.1} + \frac{5!.6.7}{5!.2} = \frac{3}{1} + \frac{42}{2} = 3+21=24$