Question: Solve the problem
maxx,y,z 2x - 2y + z s.t. x2 + y2 + z2 = 9
by the method of Lagrange multipliers. Use the sufficient second-order conditions for a strict maximum to determine which of the two solutions to the system of first-order conditions yields a maximum. Verify that this is correct by comparing the values of the objective function in both cases.