If a line passes through the points $$(9, 1)$$ and $$(9, 6)$...

Question Analysis
This question tests the student's ability to determine the slope of a line given two points. The points provided have the same x-coordinate, indicating a vertical line.

Key Concept Explanation
The slope of a vertical line is undefined because the change in x (denominator in the slope formula) is zero, leading to division by zero.

Step-by-step Solution
1. Identify the coordinates: and