用均值不等式求函数的最值.应注意三个必要条件:即一正、二定、三相等.其中“正数”、“相等”条件容易获得,而要获得“定值”条件却常常被设计为一个难点,它需要一定的灵活性和变形技巧.下面举例谈谈常用构造定值条件的技巧. Use the mean inequality to find the maximum value of the function. It should pay attention to three necessary conditions: one positive, two fixed, three phases, etc. The “positive” and “equal” conditions are easy to obtain, and you want to get the value of “” The "conditions are often designed as a difficult point, and it requires some flexibility and deformation techniques. Here are some examples of techniques for constructing constant conditions.