A: The content of compulsory education mathematics elective examination makes up for the limitations of compulsory courses in content and knowledge breadth and depth. On the one hand, the content of elective courses expands or deepens the content of compulsory courses to promote students' understanding and mastery of knowledge; On the other hand, it can develop students' skills and help to improve students' ability and apply what they have learned. Taking Vieta's Theorem as an example, after learning a formula for finding the roots of a quadratic equation, the relationship between the roots and coefficients of a quadratic equation, that is, Vieta's Theorem, is introduced in the first volume of the ninth grade mathematics textbook. This is a part of the learning content chosen for students who have the spare capacity to study. Vieta's theorem is a generalization and deepening of the discriminant knowledge of the roots of quadratic equations in one variable, and its application is more flexible. It is closely related to the discriminant of the root of a quadratic equation with one variable. The discriminant of roots is a necessary and sufficient condition for judging whether an equation has real roots, and Vieta theorem explains the relationship between roots and coefficients. No matter whether the equation has real roots or not, Vieta's theorem can quickly find the relationship between the roots of two equations, so Vieta's theorem is widely used and embodied in elementary mathematics, analytic geometry, plane geometry and equation theory.