@900sit-upsaday I, for one, am starting to downvote more. I'm also using my $5$ delete votes (and I'm using my closevotes strategically). A visit to Uber-meta (no umlaut on my keyboard, and I don't feel like internationalizing my layout) in addition to what 900 has said knocked some sense into me.
@pourjour deg(P)=deg(QD+R)=deg(QD)=deg(Q)+deg(D), so deg(Q)=deg(P)-deg(D) which is less than or equal to m-(n+1), since deg(P) is less than or equal to m and deg(D)=n+1