在数学问题中,常出现“x1∈(a,b),■x2∈(c,d)使得f(x1)=f(x2)成立”;“x1∈(a,b),■x2∈(a,b)使得f(x1)≥f(x2)成立”;“■x1∈(a,b),■x2∈(c,d)使得f(x1)≥f(x2)成立”;“■x1∈(a,b),x2∈(c,d)使得f(x1)≥f(x2)成立”等形式的命题,这些问题学生在解题时往往不能正确区分每一种情况之间的区别而造成解题失误.而 In mathematical problems, it often happens that “(x, y) = f (x2) holds for” xx ∈ (a, b) , ■ x2 ∈ (a, b) such that f (x1) ≥ f (x2) holds for “x” ∈ (a, b) (x1) ≥ f (x2) holds “” and other forms of proposition, these students in the problem-solving Often it is not possible to correctly distinguish between the differences in each case and to cause problems in the solution