Extended b-metric-preserving functions

Abstract

In this paper, we introduce a couple of classes of functions, denoted by DU and EB. We present the relationship between them and other known classes. Also, we show that the elements of the class EB, are amenable and quasi-subadditive functions (Theorem 2.14). Finally, in the Theorem 2.20, we establish that the graphic of these elements is contained in the region proposed by J. Dobos and Z. Piotrowski(see [8]).