So putting it together, the user is asking for a free PDF that teaches English using one formula or method. The task is to create a text explaining this formula in English, probably for someone who wants to learn English without paying or needing special materials.
I should check if there are any common misconceptions about learning English for free. Maybe that it's not effective without paid courses, but the reality is that consistent practice with free resources can be just as good.
Okay, time to start drafting the actual text based on all that.