point(s) of the function. If you have three-dimensional graphing software, graph the function with a domain and viewpoint that reveal all the important aspects of the function. 5. f (x, y) = x2 + xy + 12 + y 6. f (x, y) = xy - 2x - 2y - x2 - y2 11. f(x, y) = x3 - 3x + 3xy? 14. f(x, y) = y cos x 19. f(x, y) = y2 - 2y cos x, -1 5 x $7