应用均值定理求最值是高一教学的一个难点,也是高考的一个重点。教师在讲解均值定理a+b/2≥ab~(1/2)(a,b为正数)求最小值时,强调a,b为正数,ab为定值,当且仅当a=b时取等号,简单总结为“一正,二定,三等”。如果题目“三条件”都具备时学生用均值定理当然不会出差错,但当等号不成立时,即称均值定理失效,这样的题目对高一的学生来说是一个难点,并且教材 Applying the mean value theorem to seek the highest value is one of the difficult teaching, but also a focus of the college entrance examination. Teachers in explaining the mean theorem a + b / 2≥ab ~ (1/2) (a, b is a positive number) when seeking the minimum value, emphasizing a, b is positive, ab is a fixed value if and only if a = b take equal sign, simply summed up as “a positive, two fixed, three ”. If the subject “three conditions ” are available when students use the mean theorem, of course, does not go wrong, but when the equal sign is not established, the mean value theorem lapsed, so the topic for a freshman is a difficult task, and textbooks