For example, the intersection of quadratic function image and x axis; In analytic geometry, the problem of the number of intersections between straight lines and curve images is solved by the simultaneous representation of straight lines and curve equations.
When I was in high school, my teacher didn't talk about the problem of finding the domain by discriminant, which means that this kind of problem can be solved by other methods. The discriminant evaluation domain method is relatively simple and does not require much skill, but sometimes it requires a lot of calculation and has certain applicable conditions.