2.
(a) Find an equation of the tangent plane to the surfacex4 +y4 +z4 = 18 at (2, 1, 1). Find aderivative in direction (2,2,1) at point (2,1,1). (b) Use Lagrangemultipliers to ï¬nd the minimum and maximum values of f(x,y,z) = 8x+ y + z on the surface x4 + y4 + z4 = 18.
