Find the Local Maximum, and Minimum Value and Saddle Points $$f ( x , y ) = x ^ { 2 } - x y + y ^ { 2 } - 9 x + 6 y + 9$$

Short Answer

Find the local maximum, and minimum value and saddle points of the function.
$$f ( x , y ) = x ^ { 2 } - x y + y ^ { 2 } - 9 x + 6 y + 9$$