Based on the two-parameter family nature of X-ray clusters of galaxies obtained in a separate paper , we discuss the formation history of clusters and cosmological parameters of the universe .
Utilizing the spherical collapse model of cluster formation , and assuming that the cluster X-ray core radius is proportional to the virial radius at the time of the cluster collapse , the observed relations among the density , radius , and temperature of clusters imply that cluster formation occurs in a wide range of redshift .
The observed relations favor the low-density universe .
Moreover , we find that the model of n \sim - 1 is preferable .