and all points (x,y) at which they occur on the set D = {(x, y): x +) 6) Use Lagrange multipliers to find the maximum and minimum values and points (x,y,z) at which they occur, of f(x, y,z) = x2 + 2yz + 3z subject to the constraints x + y + z = 1 and x - y + 2z = 2