Find the gradient vector of the function  at the point (2, 2).

If what is/are the local maximum value/values of  f. Only write the number/numbers separating by "," . If there is no maximum value answer "no"

Find the tangent palne to the surface at in form

If what is/are the local minimum value/values of Only write the number/numbers separating by "," if there is no minimum value answer "no"

If what is/are the value/values of   at the saddle point. Only write the number/numbers separating by "," if there is no saddle point answer "no"

  is the rate of changes of f.

If

Stae the first stationary point in format. After calculating all stationary points arrange them in ascending order(lowest first) according to the x coordinate. Then write only the first point with brackets (without any white space).