近年来,各地升学考试和竞赛考试中,有不少数学试题虽然难于课本,活于课本,但又源于课本,这就要求同学们能活学活用课本知识。今介绍一道课本习题在解几道考试题中的运用。 In recent years, many local mathematics examinations and competition examinations have been difficult to teach textbooks and live in textbooks, but they also originate in textbooks. This requires students to use the knowledge of textbooks to study and use them. This paper introduces the use of a textbook exercise in solving several test questions.