To find the domain of the function \( g(x) = \frac{5x + 3}{9x - 1} \), we need to determine the values of \( x \) for which the function is defined. The function is undefined when the denominator is zero. Therefore, we need to solve the equation \( 9x - 1 = 0 \) to find the values of \( x \) that make the denominator zero and exclude them from the domain.
Step 1: Identify the Denominator
The function given is:
\[
g(x) = \frac{5x + 3}{9x - 1}
\]
To find the domain, we need to identify the values of \( x \) that make the denominator zero.
Step 2: Solve for Undefined Values
Set the denominator equal to zero and solve for \( x \):
\[
9x - 1 = 0
\]
Solving for \( x \):
\[
9x = 1 \implies x = \frac{1}{9}
\]
Step 3: Determine the Domain
The function \( g(x) \) is undefined at \( x = \frac{1}{9} \). Therefore, the domain of \( g(x) \) includes all real numbers except \( x = \frac{1}{9} \).
Final Answer
The domain of \( g(x) \) in interval notation is:
\[
\boxed{(-\infty, \frac{1}{9}) \cup (\frac{1}{9}, \infty)}
\]