Answer
$3 \sqrt 7$
Work Step by Step
The geometric mean of two numbers can be found using the following proportion:
$\frac{a}{x} = \frac{x}{b}$, where $a$ and $b$ are positive numbers and $x$ is the geometric mean.
Let's plug in our numbers:
$\frac{7}{x} = \frac{x}{9}$
Use the cross products property to get rid of the fractions:
$x^2 = 63$
Rewrite $63$ as the product of a perfect square and another factor:
$x^2 = 9 • 7$
Take the positive square root of each factor to solve for $x$:
$x = 3 \sqrt 7$
