Use the Horizontal Line Test to Determine If the Function $f ( x ) = \sqrt { 81 - x ^ { 2 } }$

Multiple Choice

Use the horizontal Line Test to determine if the function is one-to-one and so has an inverse function.

$f ( x ) = \sqrt { 81 - x ^ { 2 } }$

A) f is one-to-one
B) f is not one-to-one
C) cannot be determined