This deals with summation methods for generating functions...

Let Ar = C(2,2) + C(3,2) + ... + C(r+2,2). Find the generating function for Ar and use it to evaluate Ar.

b) Do the same for Br

Let Br = C(n,n) + C(n+1,n) + ... + C(n+r,n) where n is a given positive integer.

So for part b I need to find a generating function for Br and use it to evaluate Br.

Any help please I'm not sure how to form a generating function, and I missed this day of class, and this is the only problem on these summation methods.