Find All Numbers for Which the Rational Expression Is Not $$\frac { x ^ { 2 } - 81 } { x ^ { 2 } - 7 x + 12 }$$

Multiple Choice

Find all numbers for which the rational expression is not defined.
- $$\frac { x ^ { 2 } - 81 } { x ^ { 2 } - 7 x + 12 }$$

A) $x = 0$
B) $x = 9$ and $x = - 9$
C) $x = - 3$ and $x = - 4$
D) $x = 3$ and $x = 4$