Which sentence is not formal mandate formulation?
compartan sus ideas.
participen en la reunión.
investiguen y escriban.
muestren iniciativa.

Explanation:

It looks like they're all formal commands.

We use formal commands when we are talking to someone we don't know very well. It might be our professor, our boss, or simply an older person. Someone we want to show respect to. How do we form a formal command?

We have a singular and a plural form. For singular form, we will use USTED ( third person singular form ) and for plural, we will use USTEDES ( third person plural form ) When it comes to verbs and its tense, it's always in the present SUBJUNCTIVE tense.