Formal:
* Vous avez commis une erreur. (You have committed an error.) - This is the most formal and direct way to say it.
* Vous avez fait une erreur. (You made a mistake.) - This is slightly less formal than the first option.
Informal:
* Tu as fait une erreur. (You made a mistake.) - This is the informal way to say it, used when addressing someone you know well.
* T'as fait une erreur. (You made a mistake.) - This is the very informal version, often used among friends.
More specific phrases:
* Vous vous êtes trompé(e). (You are mistaken.)
* Il y a une erreur. (There is an error.)
* Votre calcul est incorrect. (Your calculation is incorrect.) - This is useful when referring to a specific mistake.
Important note: In French, it's generally considered polite to avoid directly blaming someone for an error. It's better to use a more neutral tone, such as suggesting a correction or politely pointing out the mistake.
For example:
* "Je crois qu'il y a une erreur dans ce calcul." (I believe there is an error in this calculation.)
* "Pourriez-vous vérifier cela ? Il me semble qu'il y a une erreur." (Could you please check that? It seems to me that there is an error.)