标题中所说的的“反函数法”,是指利用求反函数的定义域来得出原来函数值域这样一种求函数值域的方法。该方法有较大的局限性,它只适用于所给函数是一一映射(即存在反函数)的情况,而且仅当从y=f(x)解出x=f~(-1)(y)的变形过程中y取值范围不变时方才有效。鉴于“反函数法”的这些缺点,本文提出一个替代的办法,就是运用方程观点,将函数式视为关于x的方程(化 The “inverse function method” mentioned in the title refers to a method of finding the range of the original function by using the definition domain of the inverse function. This method has a big limitation, it only applies to the case where the given function is a one-to-one mapping (that is, there is an inverse function), and only if x=f~(-1) is solved from y=f(x) ( In the deformation process of y), the value range of y does not change until it is valid. In view of these shortcomings of the “inverse function method”, this paper proposes an alternative approach, that is, using the equation view, the functional formula is regarded as an equation about x.