Determine the global extreme values of the function f(x, y) = x^2 + y^2 - 2x - 4y on the following domain: x >= 0, 0 <= y <= 3, y >= x.
Find the minimum value of f (x, y, z) = x^2 + y^2 + z^2 subject to two constraints, x + 2y + z = 3 and x - y = 4.
