Why can B2-4ac judge how many points of intersection of quadratic equation and quadratic function with number axis?
This discriminant is derived. The root of quadratic equation can also be regarded as the solution of quadratic function when y=0. Quadratic functions are like parabolas, which can have at most two solutions or no solutions. When it is greater than zero, it has two intersections with the X axis; When less than zero, there is no intersection; When it is equal to zero, there is only one intersection.