User:Nullterminiert/sandbox

$$n! = \prod_{k=1}^n k$$ $$\frac {n!}{(n+1)!}=\frac{\prod_{k=1}^{n+1} k}{\prod_{k=1}^n k}=\frac{\prod_{k=1}^{n} k \cdot \left(n+1\right)}{\prod_{k=1}^n k}$$