Détendre belong to the 3
rd group. Détendre is a common french verb.
Détendre is conjugated the same way that verbs that end in :
-re
Détendre is conjugated with
auxiliary avoir.
Détendre verb is
direct transitive.
French verb détendre can be conjugated in the reflexive form:
Se détendre
Détendre verb is a direct transitive verb, so passive voice can be used.