异阶导函数揭示变化速率，展现函数之内在联系。终极三国哪个app能看

　　In a class room, a girl is sitting on the desk, solving a math quiz. If she cannot solve it in time, a horrible thing is likely to happen. The clock is ticking but the quiz is not likely to be solved. And her mechanical pencil breaks down. However she has to solve the quiz.