13.3  
  Find the equation of the plane perpendicular to 
-(Overscript[i,  ->])  + 
      4  (Overscript[j,  ->])  - (Overscript[k,  ->])   and passing through the point (3, 0, 1).

14.3 
Find the differential of f (x, y) = 
      (x^2) + (y^3) at the point
(1, 2) . 
        Use it to estimate f (0.98, 2.02).