Jensen不等式[1]:若函数y=f(x)是(a,b)上的凸函数,则对任意x_1,x_2,…,x_n∈(a,b)都有f(x_1+x_2+…+x_n/n)≤f(x_1)+f(x_2)+…+f(x_n)/n.其中等号当且仅当x_1=x_2=…=x_n时成立.Jensen不等式反映了凸函数的一个基本性质,它有着极其广泛的应用.本文中我们利用此不等式 Jensen’s inequality [1]: If the function y = f (x) is a convex function on (a, b), then for any x_1, x_2, ..., x_n∈ (a, b) x_n / n) ≤ f (x_1) + f (x_2) + ... + f (x_n) / n, where equals sign if and only if x_1 = x_2 = ... = x_n. Jensen’s inequality reflects a basic Nature, it has a very wide range of applications.In this paper we use this inequality