在证明不等式■f(xi)≥m或■f(x_i)≤m(m为常数)时,往往需要找一个所谓的“桥函数”g(x),从而可得到一个局部不等式f(x)≥g(x)或f(x)≤g(x)。然后由x分别取x_1,x_2,…,x_n得到n个不等式相加,即可使原不等式得到证明。如何确定这个局部不等式中的“桥函数”?这是证明这类不等式的关键。笔者经过探究,总结出了三种有效的方法:一是利用曲线在其割线或切线的同一 When proving that the inequality ■ f (xi) ≥m or ■ f (x_i) ≤m (where m is a constant), it is often necessary to find a so-called “bridge function” g “(x) such that a local inequality f x) ≥g (x) or f (x) ≤g (x). Then by x respectively x_1, x_2, ..., x_n get n inequalities add, you can make the original inequalities proved. How to determine the ”bridge function" in this local inequality? This is the key to prove this type of inequality. After exploring, the author summed up the three effective methods: First, the use of curves in the secant or tangent of the same