由已知的函数关系式f[φ(x)]求f(x),进而求f〔ψ(x)〕的问题,比较抽象,不少学生感到无从入手。现介绍一些常用解法。一、定义法例1 已知f(x-1)=3x~2-8x+10,求f(x)及f(x+a)。分析 f(x-1)是以(x-1)为自变量的函数,欲求其对应关系,可拆项、添项,将已知表达式配凑成关于(x-1)的多项式。 The problem of finding f(x) from the known functional relationship f[φ(x)] and then f(ψ(x)) is rather abstract. Many students feel that they cannot start with. Now introduce some common solutions. First, the definition of the law 1 Known f (x-1) = 3x ~ 2-8x +10, seeking f (x) and f (x + a). The analysis f(x-1) is a function with (x-1) as an independent variable. For the correspondence, the detachable term and the added term, the known expression is assigned to a polynomial about (x-1).