2. Use Lagrange multipliers to find the constrained critical points of f subject to the given constraints. - a) f( x, y, z) = x y z , x + y+ Z= 1. - - b) f ( x,y) = x2 + 2y - z2, 2x - y = 0, y+ z=0 c) f( x,y,z) = x, x+ +