在研究指数函数y=ax的图像和某些性质时,课本上是以a=2代表a>1的情况．其实这也符合人们的“从特殊到一般”的认知规律．不过a=2只能在某些方面代表a>1的情况．如:定义域、值域、单调性与y轴交点等方面．但并不能代表所有情况．比如研究函数y=ax(a>1)的图像与直线y=x的交点情况时,就不能用y=2x代表．课本等学习资料上经常能看到,图1中分别 When studying the image and some properties of the exponential function y=ax, textbooks use a=2 to represent a>1. In fact, this is also in line with people’s “from special to general” cognitive laws. However, a=2 can only represent a>1 in some aspects. Such as: domain, value domain, monotonicity and y-axis intersection and other aspects. But it does not represent all situations. For example, when the intersection of the image of the function y=ax(a>1) and the straight line y=x is studied, it cannot be represented by y=2x. Textbooks and other learning materials can often be seen in Figure 1