Hi guys, can anyone please tell me the combinatorial proof of P(n+1, r) = P(n,r) + P(n,r-1)?
That is not true of permutations. Let $\displaystyle n=10~\&~r=4$
$\displaystyle \mathcal{P}(n+1,r)=7920$ while $\displaystyle \mathcal{P}(n,r)+\mathcal{P}(n,r-1)=5760$
Is true for combinations $\displaystyle \mathcal{C}(n+1,r)= \mathcal{C}(n,r)+ \mathcal{C}(n,r-1) $.