Hi,
I don't understand what is the coefficient of x^r for the generating function (1/(1-x))^n
In the book, it's n+r-1 choose r
In the lecture, it's n+r-1 choose r-1
In the quizz, it's something different.. What's the correct formula ?
Thank you !
In the lectures we computed the coefficients of degree n of (1-x)^r which is {r+n-1}\choose {n} which is {r+n-1}\choose{r-1}