在诺窪塞洛夫著初等代数特别教程§51中有两个我们所熟知的不等式:一个是关于中凹函数的定理;所谓中凹函数f(x),就是对于其定义区域内任二相異的数x_1,x_2均有f((x_1+x_2)/2)<(f(x_1)+f(x_2))/2。如果不等式的方向常相反就叫做中凸函数。 There are two well-known inequalities in Novocerov’s special elementary algebra tutorial, §51: one is the theorem about the concave function; the so-called concave function f(x) is any two-phase in its defined area. The different numbers x_1, x_2 all have f((x_1+x_2)/2)<(f(x_1)+f(x_2))/2. If the direction of inequality is often the opposite, it is called the convex function.