.
Find the positive value of X if the geometric mean between 1 and 9 is X.
~~~~~~~~~~~~~~~~~~~~~~
The formulation in the post is INCORRECT.
The correct formulation is THIS:
Find the value of X if the geometric mean of 1 and 9 is X.
1. Geometric mean is defined for positive (non-negative) values of the input parameters ONLY.
2. By the definition, geometric mean is always positive (non-negative) number.