EX 10/02

retour

\[A = \frac{n!}{(n-2)!} = \frac {n \cdot (n-1) \cdot \cancel{(n-2)!}} {\cancel{(n-2)!}} = n(n-1).\] \[B = \frac{(n-1)!}{(n+2)!} =\frac{\cancel{(n-1)!}}{(n+2)\cdot (n+1) \cdot n\cancel{(n-1)!}} = \frac 1{(n+2)(n+1)n}.\] \[C = \frac{n!}{(n+1)!} = \frac{\cancel{n!}}{(n+1)\cdot\cancel{n!}} = \frac 1 {n+1}.\]

retour

code : 2732