关于由两个不等号连接的不等式求解、证明以及与不等式有关的这类命题,都有一个共同的特征,那就是要思考和分析连接不等号的三个式子的大小关系.如果三个式子的大小关系形如a≤f(x)≤b,那么三个式子a、f(x)、b所对应的值就可看作数轴上的三个点,其中有两个定点(对应a、b)和一个动点(对应f(x)),当我们把这 There is a common characteristic about the solution of inequalities connected by two inequalities, the proofs and the propositions related to inequalities, that is, to think about and analyze the relationship between the sizes of the three inequalities, The relationship between the size and the size of a ≤ f (x) ≤ b, then the three equations a, f (x), b corresponding to the value of the axis can be seen as three points, of which two fixed point (corresponding to a, b) and a move point (corresponding to f (x)) when we take this