由已知条件求函数f(x)的表达式,是函数这部分教材的一个方面的问题,它不仅能深化函数概念,还常常联系着一些重要的解题方法和技巧。因此,对这个问题进行探讨是很有必要的。兹将一些常用方法,归纳于后: 一、待定系数法例1 求实系数一次函数f(x),使f{f[f(x)]}=8x+7. 分析:要求一次函数f(x)=ax+b,只要能求出系数a与b就行了,因此,归结到确定系数a与b的值。 The expression of the function f(x) is known from the known conditions. It is an aspect of the function of this part of the teaching material. It not only can deepen the concept of the function, but also often connects with some important problem-solving methods and techniques. Therefore, it is necessary to discuss this issue. Here are some commonly used methods, summed up in the post: First, the undetermined coefficient of the law of the first instance of a real function f(x), so that f{f[f(x)]}=8x+7. Analysis: requires a function f(x) =ax+b, as long as the coefficients a and b can be found, it comes down to determining the values ​​of the coefficients a and b.