Switching from formal to informal in midsentence?
One of the practice questions I got was "Por favor escribe tu libro". Is it correct to switch from formal verb conjugation (escribe) to informal possessive (tu) in one sentence? Shouldn't it be "Por favor, escribes tu libro" or "Por favor, escribe su libro"?
In this case 'escribe' isn't the usted conjugation of the verb but its imperative form. Look here: http://conjugator.reverso.net/conjugation-spanish-verb-escribir.html . The "usted imperative" would be 'escriba'