1. Consider a quadratic form: Q(x, y) = ax2 + v2xy + cy2 (a * 0). a. Show that if Q(x, y) is positive definite, then a > 0 and c > 0. b. Suppose that a > 0 and ac = . What is the definiteness? c. Suppose that c = -1. Find the range of value a in which Q(x, y) is negative definite