Find the maximum and minimum values of the function f (x, y) = 3x + 4y on the circle = x ² + y ² = 1

Find the greatest and smallest values that the function f(x, y) = xy takes on the ellipse x ² /8, y ² /2 =1,

Find the absolute maxima and minima of the function f(x, y) = 48xy - 32x ³ -24y ² on the rectangular plate 0 < x < 1, 0 < y < 1.

Find the local extreme values of the function f(x, y) = xy – x ² - y ² -2x – 2y + 4.

Classify as to maxima minima, or saddle points.