3. Use Lagrange multipliers to find the maximum and minimum values of f subject to the given constraint. 1 (a) f(x,y) ==+= 1 1 1 + x Y x2 y2 2 (b) f(x, y, z) = xyz, = 1 + y²+z² = 3 (c) f(x, y, z) = x² + 2y²+3z2, x+y+z = 1, x-y+2z = 2