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当一个问题因为某种量的不同,而有可能引起问题的结果不唯一时,就需要对这个量的各种情况进行分类讨论,使问题得到全面的解答,这就是数学中的分类讨论思想。一、有理数中的分类思想例1如图1,在数轴上表示到原点的距离为3个单位的点有()。A.D点B.B点C.A点和D点D.B点和C点分析:到原点的距离等于3个单位的点,可能在原点的左侧,
When a problem is caused by a certain amount of difference and the result is not the only one that may cause the problem, we need to classify and discuss the various situations of this amount so that the problem can be fully answered. This is the categorical discussion in mathematics. First, rational numbers in the classification of ideas Example 1 As shown in Figure 1, on the number axis to the origin point to the distance of 3 units of points (). A.D point B.B point C.A point and D point D.B point and C point analysis: the distance to the origin is equal to 3 units of points, may be in the left side of the origin,