For positive integers http://stuff.daniel15.com/cgi-bin/mathtex.cgi?r, define http://stuff.daniel15.com/cgi-bin/ma...%20%28x-r+1%29

Show that http://stuff.daniel15.com/cgi-bin/ma...line%7Bn%7D%7D

It looks so similar to http://stuff.daniel15.com/cgi-bin/ma...%7Bn%7D%7Bn%7D but I have no idea how to prove it :(

Any ideas?