我在一次高三数学复习测试中选用了这样一道题:“设函数f(x)=x2+x+a(a∈R*)满足f(n)0,判断f(n+1)的符号.”结果大多数学生没有做出来,甚至有许多学生在听了老师讲解后还是不得其解.事后,我反复思考,这是一道中等难度的题目,为什么会出现这种情况呢?经仔细了解发现:学生不善于 In a high school mathematics review test, I chose such a question: “Let the function f (x) = x2 + x + a (a∈R *) satisfy f (n) 0 and judge the sign of f (n + 1). ”As a result, most of the students did not make it out and many of them even got puzzled after listening to the teacher’s explanation. Afterwards, I repeatedly thought that this was a problem of medium difficulty. Why did this happen? Students are not good at it