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?
Edit: I gave them the Tuesday before spring break until the Thursday after. I didn’t want it to be right before or right after.
When I say normal I mean giving take home exams.
Unless you explicitly stated in the exam that they had to show their work with their answer or fail, even if the answer was correct, then I say pass them. It’s on you to be specific as to what you want to see on the exam. Maybe they worked it out on scratch paper and didn’t turn that part in with the exam?