用判别式法求形如y=(dx2+ex+f)/(ax2+bx+c)的函数的值域,方便快捷.更重要的是,判别式法是帮助学生体会函数方程思想、化归思想的绝佳素材.但笔者发现很多同学滥用这种方 It is convenient and quick to use the discriminant method to find the value range of the function such as y = (dx2 + ex + f) / (ax2 + bx + c), and more importantly, the discriminant method is to help students to understand the function equation, The perfect material for thinking, but I found that many students abuse this party