Use the Limit Definition of the Partial Derivative to Compute $\text { Find } \frac { \partial f } { \partial x } \text { at the point } ( 9 , - 6 , - 6 ) : f ( x , y , z ) = 6 x ^ { 2 } y + 3 y ^ { 2 } + 6 z$

Use the limit definition of the partial derivative to compute the indicated partial derivative of the function at the specified point.
- $\text { Find } \frac { \partial f } { \partial x } \text { at the point } ( 9 , - 6 , - 6 ) : f ( x , y , z ) = 6 x ^ { 2 } y + 3 y ^ { 2 } + 6 z$