Identify all x-values where the graph has points
Include every x-value covered by the graph
Exclude x-values where the graph has gaps, holes, or breaks
Exclude x-values where the graph has open circles
Exclude x-values where the graph has vertical asymptotes
Exclude x-values where the graph does not exist
Write the domain in interval notation or set notation
Use brackets for included endpoints
Use parentheses for excluded endpoints
Combine all valid x-intervals into the final domain