How can I show that k and n being integers
the following is true using a combination proof.
I am not sure how to do this. on the right hand side you have the set of n object and you are and out of the set (2n-1) object you chose n-1 and multiply by the set n.
On the right hand you chose a out n of object one item a k and square it and then multiply by this k object. For as many k item you have.
But how is it shown they equal?