Please help with practice example problems 5 and 6.

5) Let f y) if G, y) # (0, 0) and f (0, 0) (x4 +6y8 ) Of Df a) Show that (0, 0) and (0, 0) exist. Dy b) Show that f is not differentiable at (O, O) by showing that f is not continuous at (O, O). 6) (v2 + w2 , u3 Use the chain rule to find D (f o g) (1, 2) for f(u, v, w) (3m -4- 2y, m3y, 2). vw, u2v + w) and