Determine the Function Value $f ( x ) = \log _ { a } x$

Multiple Choice

Determine the function value.
-Suppose $f ( x ) = \log _ { a } x$ and $f ( 9 ) = 2$ . Find $f \left( \frac { 1 } { 81 } \right)$ .

A) $\frac { 1 } { 2 }$
B) $- 2$
C) $- 4$
D) 4