文[1]通过构造二次函数,巧用判别式解决了一类问题.笔者的观点是,判别式法略嫌陈旧,这一方法仅适用于可构造二次函数类问题,缺乏生命力,难于推广.事实上,文中问题只要善用柯西不等式同样可以获解,解题过程宛若行云流水,既简且美,值得向学生介绍.柯西不等式对任意实数a1,a2,…,a Wen [1] constructed a quadratic function, using a discriminant to solve a class of problems.The author’s point of view, the discriminant method is somewhat outdated, this method is only applicable to the construction of quadratic function problems, the lack of vitality, is difficult In fact, as long as the problem can be solved by using the Cauchy inequality as well, the problem-solving process is as simple as flowing, simple and beautiful, and it is worth to introduce to students. Cauchy inequality can not be applied to any real numbers a1, a2, ..., a