What does this equation mean? Im really bad in reading those, so if somebody explained it, I would really appreciate. $f_i x,y \ge \quad\forall i\{,,\}$.Hi everyone, I have a friend in my homeschool group who accidentally discovered that her year old son can read a book better upside down rather than.Not only do PI kids read upside down, but many actually write upside down, too.Without PI this young man was unable to read or write on even Kindergarten level very frustrating for him, his parents and his teachers..By learning to read and write upside down, what did I do to myself? There’s even research specifi.y on reading and writing upside down and back to front .