A redshift magnitude relation for radiation universes

A closed formula for the relation between distance and redshift in an expanding radiation-filled universe is derived for the case of positive cosmological constant and positive space curvature. This formula is then generalized so that it is valid for all values of the cosmological constant and the three possible space curvatures. From this distance redshift formula, a generalized redshift magnitude relation is found. This latter formula is then checked by testing it with the cases expressible in terms of elementary functions.