Find the critical point(s) of the function. f(x, y) = xy + 12x - 8y +2 (Give your answer as a comma-separated list of points in the form (*,*) if needed. Express numbers in exact form. Use symbolic notation and fractions where needed.) critical point(s): Compute the discriminant D (x, y). (Express numbers in exact form. Use symbolic notation and fractions where needed.) D(x, y) =