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估值,顾名思义,就是估计一个数的近似值或取值范围.估值的方法具有实用性、渐进性、开放性等主要特征.适当的估值与精确的计算、严密的推理相辅相成.很好地掌握并灵活地运用估值的方法,是数学新课标的基本要求之一,是良好数感的重要表征,也是未来社会的公民所应具备的基本数学素养.在实数问题中,常常不需要或不能直接求出一些无理数的精确值,只需估计它们的近似值或取值范围就可以使问题得到解决.纵观近几年的各地中考题,关于实数估值的题目大致有如下几类.
Valuation, as the name implies, is to estimate the approximate value or the range of values of a number. The method of valuation has the main features of practicality, gradualness, openness, etc. Appropriate valuation and accurate calculation and strict reasoning complement each other. The mastery and flexible use of the valuation method is one of the basic requirements of the new curriculum standard for mathematics, an important representation of a good sense of numbers, and a basic mathematical literacy that citizens of the future society should have. In real-number problems, it is often not necessary or Can not directly find the exact value of some irrational numbers, only to estimate their approximate value or range of values can make the problem be solved. Throughout the past few years in the local exam questions, the topic of real number valuation are roughly the following categories.