Find the Domain of the Given Function $$f ( x ) = \sqrt { x ^ { 4 } - 81 x ^ { 2 } }$$

Multiple Choice

Find the domain of the given function.
- $$f ( x ) = \sqrt { x ^ { 4 } - 81 x ^ { 2 } }$$

A) $( - \infty , - 9 ] \cup [ 9 , \infty )$
B) $( - \infty , - 9 ] \cup [ 0 ] \cup [ 9 , \infty )$
C) $( - \infty , \infty )$
D) $( - \infty , - 9 ) \cup ( 9 , \infty )$