Let K {\displaystyle {}K} be a field, and let
be the set of all mappings from K {\displaystyle {}K} to K {\displaystyle {}K} . We consider the relation on Map ( K , K ) {\displaystyle {}\operatorname {Map} \,{\left(K,K\right)}} defined by f ∼ g {\displaystyle {}f\sim g} if there exist c , d ∈ K {\displaystyle {}c,d\in K} such that
holds for all x ∈ K {\displaystyle {}x\in K} . Show that this is an equivalence relation.