Final answer:
The equation of the line with an undefined slope through the point (5, -15) is x = 5, representing a vertical line where all points have an x-coordinate of 5.
Step-by-step explanation:
The question involves writing the equation of a line with an undefined slope that passes through a given point. In this case, the line needs to pass through the point (5, -15). A line with an undefined slope is a vertical line, which means all points on the line have the same x-coordinate. Therefore, the equation of this line is simply x = 5. This equation indicates that no matter what the y-value is, the x-value will always be 5, resulting in a vertical line on a graph.