aktivem
Aktivem is a form of the German adjective aktiv. It is the dative singular form used when the adjective carries the strong declension, typically before a masculine or neuter noun in the dative case without a preceding determiner. In the strong declension, the dative singular ending is -em, yielding aktivem.
In practice, aktivem appears in phrases such as mit aktivem Lebensstil or in aktivem Zustand. These examples
Summary: aktivem is the dative singular form of aktiv under strong declension, used before masculine or neuter
See also: German grammar, adjective declension, German declension patterns.