Find All Values of the Variable for Which the Rational $\frac { 36 x } { x ^ { 2 } - 4 x - 12 }$

Find all values of the variable for which the rational expression is undefined.
- $\frac { 36 x } { x ^ { 2 } - 4 x - 12 }$

A) 0
B) $- 6,2$
C) $- 6,6$
D) $- 2,6$