引例:从集合{1,2,3,…,10}中任取三个不同的数构成等差数列,求构成的等差数列的个数.在课外资料书上,我们经常可以看到这样一类试题,资料书上给出的参考答案通常如下:一般解若等差数列公差大于0,则数列递增,此时分类讨论有如下这些情形:d=1时,有8种情况: Example: Take any three different numbers from the set {1,2,3, ..., 10} to form the arithmetic progression, and find out the number of the arithmetic progression columns. Often we can see in the extracurricular information book A class of questions, the reference book given in the information book is usually as follows: General Solutions If the tolerance column error is greater than 0, the number of columns increases, the following discussion of classification of these situations: d = 1, there are 8 cases: