“三个二次”之间关系紧密,不可分割。高中数学中的解一元二次不等式的各种题型都要利用一元二次方程的实数根个数的情况和二次函数的图像解决。 There is a close and inseparable relationship between “three secondary”. In the high school mathematics, the solution to the problem of the quadratic inequalities of the one-variable quadratic inequalities requires the use of the number of real roots of the quadratic equation and the image of the quadratic function.