Locate the Maximum of the Function $f ( x , y ) = e ^ { - \left( x ^ { 2 } + y ^ { 2 } + 8 x \right) }$

Essay

Locate the maximum of the function.
​ $f ( x , y ) = e ^ { - \left( x ^ { 2 } + y ^ { 2 } + 8 x \right) }$ ​
Express your answer as an ordered triple. If there is more than one answer, separate them by commas.