Economics · Optimization & Convexity Theory

Which of the following statements are CORRECT about concave and convex functions in economic optimization? A. A twice-differentiable function is concave if and only if its Hessian matrix is negative semi-definite everywhere. B. A local maximum of a concave function is also a global maximum. C. Quasi-concavity of a utility function is sufficient for the standard consumer optimization problem. D. A strictly convex function has a unique global minimum.