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在求参数范围的问题中,经常需要对参数的取值范围进行分类讨论.有些讨论过程非常繁琐,技巧性也比较强.学生在解题时往往理不清思路,讨论无从下手.其实如果能抓住题目中的某些细节,以此找到解决问题的突破口,会有意想不到的收获.这里我们应注意一些特殊值,它们往往在解题中起着关键的作用.本文结合几个实例来谈一谈.一、利用特殊值缩小参数的讨论范围例1(2013年全国高考题)设函数f(x)
In the problem of seeking the parameter range, often need to carry on the classification discussion to the parameter value range.Some discussion process is very tedious, the skill is also quite strong.Students often can not understand the thought in the solution problem, the discussion can not start .In fact, if can Grasp some of the details of the problem, in order to find a breakthrough to solve the problem, there will be unexpected gains. Here we should pay attention to some special values, they often play a key role in problem solving. First, the use of special value to narrow the scope of the discussion of the parameters Example 1 (2013 National Entrance Examination) set function f (x)