I need help please

6) For the smooth function f that satisfies: 8f 5f 1,2 =9 1,2 =5 1,2 =7 f ( ) 6x( ) 6y( ) (a). Write the linear approximation of f(x, y) centered at (1,2): (a'). Write an equation of the tangent plane to the graph of f at (1,2,9): (a\"). Write an equation of the level curve of the above tangent plane to the graph of the function f at (1, 2,9) at level 2 = 9 : (b). Compute the derivative of: L,(1,2)(1+(4/ (4)2+(6)2)t,2+(6/ (4)2+(6)2)t) (b'). Compute the directional derivative at (1,2) in the direction of . Explain what this MEANS and how this is connected to (b): (c). Find a vector in the direction of maximal decrease at (1,2): (c'). Compute the 1% of maximal decrease at (1,2): (d). Find a vector in a direction of no change at (1,2): (d'). Find a parameterization of the tangent line of the level curve through (1,2): (d"=a\"). Find an equation of the tangent line of the level curve through (1,2): (e). Draw and label a sketch that includes: i) The point (1, 2), ii) The vector Vf (1, 2) , iii) The tangent line to f (x, y) = 9 , iv) A piece of the curve f (x, y) = 9 , v) The ascending gradient flow of f through (1,2). l