To find \( x \) using the geometric mean, we typically need two values. However, you've only provided one value: \( 4.2 \).
The geometric mean of two numbers \( a \) and \( b \) is given by:
\[ \sqrt{a \cdot b} \]
Since only one value is given, we cannot calculate the geometric mean without a second number. If you have another value or a specific context in which to use \( 4.2 \), please provide it so I can assist you further!