How can it be proved that Rnl(r) has (n-l-1) zeros (not counting those at r-0 and r= infinity? I tried doing this inductively but found it hard to get anywhere since the equations for Rnl(r) aren't too pretty. For instance, Rnl(r)=Anlunl where Anl= sqrt((n-l-1)!/(2n((n+l)!)^3) this last equation seems to bear a similarity with what I am supposed to prove but I am having trouble with this. Help anyone?