Thread: prove an equality

hello
negbinomial(x;k,θ)=k/x*binomial(k;x,θ)
how i can prove it??

what exactly does negbinomial(x;k,θ) mean?

Is it P(X=k) for a NegBi?

negbinomail(x;k,θ)=p(x-1,k-1)*θ^k *(1-θ)^(x-k);so that p(x-1,k-1)=combination of k-1 of x-1
Negative binomial distribution - Wikipedia, the free encyclopedia