The document discusses the simple past negative form of verbs. It states that for the verb "to be" (was, were), no auxiliary is needed - just add "not". It provides examples of changing sentences from present to past negative using "to be", like "I am in Veracruz" becoming "I wasn't in Veracruz". For other verbs, an auxiliary like "did" is needed, so "Antonio played soccer" becomes "Antonio didn't play soccer". Exercises are provided to practice changing sentences to past negative form.