我们知道,3个苹果放在2个抽屉里,必然有一个抽屉里有2个苹果.这是一个简单的事实,人们称其为抽屉原理.妙用抽屉原理,证明某些不等式,能起到比较神奇的效果.本文给出几个例子.例1已知a,b,c为正实数,a2+b2+c2+abc=4,求证:a+b+c≤3.证明由题意可知,a,b,c中必有2个不大于1,或者不小 We know that three apples in two drawers, there must be two apples in a drawer.This is a simple fact, people call it the drawer principle.Fantastic drawer principle, to prove that some of the inequalities, can play a comparison Magical effect.This article gives a few examples.Example 1 known a, b, c is a positive real number, a2 + b2 + c2 + abc = 4, verify: a + b + c ≤ 3. Proved by the title, A, b, c must have 2 not more than 1, or not small