数学附录 10凸函数: assume that a real-valued function f is defined on a convex set XoRn f is said to be convex if for any xand x?"in X, and any real number nE(0, 1), it holds that (1-λ)f(x3)+λf(x”)≥f(1)x,+x”) f is said to be strictly concave if the sign“≥” in the above inequality is replaced by">数学附录 • 10 凸函数： Assume that a real-valued function f is defined on a convex set Xn . f is said to be convex if for any x’ and x” in X, and any real number (0, 1), it holds that (1-)f(x’)+f(x”)  f((1-)x’+x”) • f is said to be strictly concave if the sign “” in the above inequality is replaced by “>