数学附录 l1拟凹感数: A function f defined on a convex set Xcr" is said to be quasi- concave,. if for any X,andx” in X and anyλ∈[0,1 f(1-x+x”)≥min{f(x3),f(x”) f is said to be strictly quasi- convex, if the sign“≥” in the above inequality is replaced with“>” 7. Any concave(strictly concave) function is quasi-concave(strictly quasi-concave), but the converse is not true.数学附录 • 11 拟凹函数：A function f defined on a convex set Xn is said to be quasi-concave, if for any x’ and x” in X and any [0, 1]: f((1-)x’+x”)  min {f(x’),f(x”)} • f is said to be strictly quasi-convex, if the sign “” in the above inequality is replaced with “>”. • 7. Any concave (strictly concave) function is quasi-concave (strictly quasi-concave),but the converse is not true