在全国各地的竞赛题和竞赛辅导题中,都有一些难度较大的选择题,用学生熟悉的常规方法推导分析,费时费力,甚至无法求解、难以取得理想成绩。而用赋值法分析求解,就比较快速准确。能用赋值法解的题目有两类,一类是线性变化的题目,代入数值计算分析就可选择结果,另一类是非线性变化的题目,要取两端和中间三个变化位置代入数值计算分析才能选出答案。 There are some difficult multiple-choice questions in competition questions and competition coaching questions all over the country. It is time-consuming and laborious to use the routine methods that students are familiar with to deduce and analyze, and it is difficult to obtain solutions and achieve satisfactory results. The analysis by using the assignment method is relatively fast and accurate. There are two types of problems that can be solved by the assignment method. One is a linearly varying problem. Substituting in the numerical calculation analysis can select the result. The other is a non-linear change problem. It is necessary to take two change positions at the two ends and the middle into the numerical calculation. Analysis can select the answer.