The line segment that is a reflection of AB over the x-axis is AB'.
The reflection of a line segment over the x-axis involves changing the sign of the y-coordinates while keeping the x-coordinates unchanged.
If your line segment is denoted as AB with coordinates A(x₁, y₁) and B(x₂, y₂), the reflection of AB over the x-axis would be A'(x₁, -y₁) and B'(x₂, -y₂).
In other words, each y-coordinate is negated to obtain the reflected image.
Below is the attached graph.