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利用导函数的正负可判断原函数的增减,反之,若已知函数的增减,亦可得出导函数的正负.根据这一特性,我们可以利用函数在某个区间内的单调性,求参数的范围.其本质是利用该区间上f′(x)≥0(≤0),将问题转化为函数最值问题求解.要确定参数的取值范围需要将函数与不等式的基础知识灵活应用.这类问题涉及知识面广,解题方法灵活多变,综合性强.下面就将这类问题的常见考查视角,举例分析.一、参数单独分离——转化为定区间内的
Using the positive and negative of the derivative function, we can judge the increase or decrease of the original function, on the contrary, if the increase or decrease of the function is known, we can also get the positive and negative of the derivative function.According to this property, we can make use of the monotonous function The essence of which is to use the f ’(x) ≥0 (≤0) in this interval to convert the problem to the most value function of the function. To determine the range of the parameter, we need to base the function on the inequality The application of knowledge flexible.This kind of problem involves a wide range of knowledge, problem-solving methods are flexible and comprehensive.Here we will examine the common viewpoints of such problems, for example analysis.One separate parameters - into a fixed interval