1.
f_x (x,y) = y^2z^3
f_y (x,y) = 2xyz^3
f_z (x,y) = 3xy^2z^2
[4 4 6].[2 -1 -1] 
= [8 -4 -6]


2.
f(x,y) = x^2+y^3 pt (2,1)
Gradient = [2x 3y^2] 
Grad(at 2,1) = [4 3]
magnitude of gradient = 
sqrt(16+9) = 5