在数学解题中常常会碰到一类需要“两头夹”来估计与估算的问题。这类问题往往带有较强迷惑性,表面的数量关系错综复杂,而且条件富有弹性难以确定,让人难以下手。而只要合理运用所谓“两头夹”策略,即针对题意中必须进行范围限制的要求,对直露或隐蔽的两个同类条件进行“放缩”处理,并有可能不断试验调整,以确定结果所在的合适取值范围,就能 In mathematics problems often encounter a need to “double-headed” to assess and estimate the problem. Such problems tend to be more confusing, the number of surfaces is intricate, and the conditions are more flexible and difficult to determine, making it hard to get started. As long as the rational use of the so-called “two-headed ” strategy, that is, for the problem must be carried out within the limits of the requirements of the direct or hidden two similar conditions “shrink ” processing, and may continue to test adjustment , To determine the appropriate range of values ​​where the result will be