对于已知割线斜率范围求参数的范围这类题目,许多资料上都是利用等价转换为另一个函数的单调性,然后再用导数解决的方法,但是对于这类题目还有更直接的方法,就是将割线的范围转化为函数切线的斜率范围,从而求得参数的范围,这种方法在许多资料上无从查证,更没有对于这种解法可行性的证明。本文主要从一个具体的例子来说明这种解法,并且给出了这种解法可行性的证明,最后对题目作了引申。 For such topics as the range of the known secant slope range for finding the parameters, many of the data are converted to the monotonicity of another function by equivalence, and then solved by the derivative method, but there is a more direct The method is to convert the range of the tangent to the slope range of the tangent of the function so as to obtain the range of the parameter. This method can not be verified in many materials and there is no proof of the feasibility of this solution. This paper mainly explains the solution from a concrete example, and gives the proof of the feasibility of this solution. At last, it extends the subject.