Scattered but important knowledge points

Function (function), first translated by Li Shanlan, a mathematician of the Qing Dynasty in China, from his book "Algebra". The reason why he translates it this way is that "where this variable is a function of another variable, then this is a function of that", that is, a function refers to the change of one quantity with the change of another quantity, or in other words, in a quantity. contains another quantity.