函数不是一种数,而是描述变化规律的一种数学模型.例如,地球每秒都在以太阳为“中心”的椭圆形轨道上前进约30千米,由此我们可以写出一个式子s=30t,其中s代表运动距离(以千米为单位),￡代表运动时间(以秒为单位).式子s=30t就是一个函数,它揭示了s和t之间的数量关系,从而描述了地球公转的运动规律. A function is not a number, but a mathematical model that describes the law of change.For example, every second the Earth marches about 30 kilometers on an oval orbit with the sun as the “center”, so we can write one S = 30t, where s is the distance traveled in kilometers and £ is the movement time in seconds. The formula s = 30t is a function that reveals the quantitative relationship between s and t , Thus describing the law of movement of the Earth’s revolution.