I gave my students a take home exam over spring break. (This is normal where I teach) One of the questions was particulary difficult. It came down to a factor of three in the solution. That factor inexplicably appeared with no justification on many of their exams. I intend to have the students I suspect of cheating come to my office to solve the problem on the board. What would you do?
Do nothing, first of all any homework is open book, no buts
Second of all it comes down to not being a dick
You do realise that even if they do cheat, since its a take home you likely won’t face any negative consequence, its just a win win in general