At What Point Is the Following Function a Local Maximum $$f ( x , y ) = 3 - 8 x + 12 y - 4 x ^ { 2 } - 6 y ^ { 2 }$$

At what point is the following function a local maximum?
$$f ( x , y ) = 3 - 8 x + 12 y - 4 x ^ { 2 } - 6 y ^ { 2 }$$