学习函数,我们要从数和形两个方面来分析.函数的“形”———即图象,可以帮助我们直观地看到“数”所反映的一些几何特征,但精确度不够.我们知道,在数学里,往往不能通过观察就直接下结论.函数的“数”———即函数的表达式,不能让我们直观地看到一些结论,但从数入手,可以精确地 Learning function, we must analyze from the two aspects of number and shape. The “shape” of function—that is, the image, can help us to intuitively see some geometric features reflected by “number”, but the accuracy is not enough. We We know that in mathematics, we can’t directly conclude by observing. The “number” of a function—that is, the expression of a function—does not allow us to see some of the conclusions intuitively, but from the beginning, we can accurately