Estimate the Derivative of the Function $f ( x ) = \frac { x ^ { 2 } } { 2 } - \frac { x ^ { 3 } } { 12 }$

Short Answer

Estimate the derivative of the function $f ( x ) = \frac { x ^ { 2 } } { 2 } - \frac { x ^ { 3 } } { 12 }$ at the point $x = - 1$ .
​
Please round your answer to the nearest hundredth.