Answer:
When you cross a boundary line between two regions, you will have left one region and entered another. The boundary line is typically a curve or a line that separates the two regions. You can identify the boundary line by looking at the equation of the function that defines the regions. The boundary line will be the set of points where the equation is true for both regions. For example, if the equation is y = x² and the two regions are above and below the x-axis, then the boundary line is the x-axis itself, since it is the set of points where y = 0 for both regions. When you cross the x-axis, you will have left one region and entered the other.
Step-by-step explanation: