Generally, according to the actual problem, the quadratic function relationship that meets the meaning of the question is listed, and then the maximum or minimum value is judged according to its opening direction or positive and negative quadratic terms; In some practical problems, the maximum value is not necessarily the ordinate of the vertex, but the maximum or minimum value should be calculated according to the range of independent variables and the changing trend of function values.

Sometimes it is combined with linear function or inverse proportional function, such as letting you calculate the minimum sum of two line segments, or finding the coordinates of a point when the perimeter of a triangle is the smallest, and so on. This is generally based on the knowledge of "the shortest line segment between two points", and two line segments are transferred to the same straight line by using axial symmetry. After finding the desired point, calculate the coordinates.