Two Observations on Groups with Engel Elements

Аннотация

We answer (in the negative) Questions 16.15(a) and 17.3 of The Kourovka Notebook: “Is the set of all restricted Engel elements a subgroup in every group?” and “Is it true that a group is binary nilpotent if any 4-element subset therein contains two elements generating a nilpotent subgroup?”