Hello, I need help answering these questions with explanation

l. (l5pt) Let f(:c,y) = ln(st'2 + y). Compute the directional derivative D l>f(_2s _ ) 2'2 113' 5'3 _ 9' change in the direction of fastest decrease for f at the point (3, 2). 2. (l5pt) Consider the function f(a:,y) = . Compute the rate of 3. (10pt) Consider the surface With equation: 332+yz=5 (a) Find a function F(m,y,z) so that the above surface is a level surface for the function F. (b) Find a non-zero vector perpendicular (normal) to the given sur- face at the point (2,1,1). (c) Find the equation of the tangent plane to the given surface at the point (2, 1,1). 4. (l5pt) Find and classify the critical points of f(a:, y) = 3:3 3363} + y3 as to Whether each one of them is a local minimum, a local maximum or a saddle point