函数是近代数学研究的重要对象,是研究近代科学技术和解决生产实际问题必不可少的工具.函数研究的是变量之间的相依关系和变化规律.设在某变化过程中有两个变量x和y,变量y随着变量x一起变化,而且依赖于x.当变量x每取一个确定的值,变量y都有唯一确定的值与之对应,那么就称变量x、y之间的关系为函数关系,y叫做x的函数,记作y=f(x).其中x叫做自变量,x的变化范围称为函数的定义域;y叫做因变量,与x相对应的y的值叫做函数值,其全体 Function is an important object in the study of modern mathematics. It is an indispensable tool for studying modern science and technology and solving practical problems in production. The function studies the dependence of variables and the law of change. There are two variables x in a certain change process. With y, the variable y varies with the variable x, and depends on x. Whenever the variable x takes a certain value, the variable y has a uniquely determined value corresponding to it, then the relationship between the variables x, y is called For a functional relationship, y is a function of x, denoted as y=f(x). x is called an argument. The range of change of x is called the domain of the function; y is called the dependent variable, and the value of y corresponding to x is called Function value, its total