在一个含有多个变元的式子(多项式或等式或不等式)中,若交换其中的两个变元其式子不发生改变,则称此式关于这两个变元是对称的,若交换其中任意两个变元其式均不发生改变,则称此式关于所有变元是对称的.利用对称解题是一种重要的思想,其中利用对称可巧妙简捷地求解一类最值问题,看下面的两例. In a formula with multiple arguments (polynomials or equations or inequalities), if the two variables in the formula are not changed, the formula is symmetric about the two arguments. If The exchange of any two variables of which the formula does not change, then this type is symmetric about all the arguments. The use of symmetric problem-solving is an important idea, the use of symmetry can be clever and simple solution to a class of most value problems Look at the following two cases.