求函数的解析式，就是求两个变量之间的函数关系。它包括求出两个变量之间的对应法则和函数的定义域。 下面介绍几种求函数解析式的常用方法。 一、代入法 此法一般用于求复合函数的解析式。若ｙ＝ｆ（ｕ），ｕ＝ｇ，求以ｘ为自变量的函数ｙ的解析式，其方法是把 ｖ＝　（ｘ） The analytical expression of a function is to find the functional relationship between two variables. It involves finding the correspondence between two variables and the domain of the function. The following describes several commonly used method to find the analytical function of the function. First, substitution method This method is generally used to find the analytic function of a compound function. If y=f(u),u=g, find the analytical formula of the function y with x as its independent variable by v=(x)