Transformation is an important mathematical thought in senior high school, that is, the content that you can't do, don't understand and have no idea is transformed into the content that you can do, have ideas and have seen through certain methods. For example, in junior high school, we learn to solve binary linear equations by eliminating elements and transforming them into linear equations. In fact, solving problems in high school is such an idea. The given conditions cannot be used directly, but must be transformed into conditions that are useful to you.