if X and Y are discrete RVs with pmf where x and y are .
I want to find the value of a.
I know that I need to show that the pmf sums up to 1.
since x and y are non negatve: 0<=x+y<=k
here i am getting confused in where x and y range from.
can anyone help me how to solve this?
Refer to the section on series of binomial coefficients
Binomial coefficient - Wikipedia, the free encyclopedia
and additionally from binomial theorem
So using this formula, we can write