Question

A line that includes the points (–7,10) and (r,6) has an undefined slope. What is the value of r?

Answer 1

-7

Explanation:

This one is tricky if you aren't sure what undefined means. It means that the slope points straight up and downwards. So, it must have the same "x" coordinate at every single point on the line.

To see what that looks like mathematically, just use your slope equation. Since the bottom evaluates to 0, it is undefined.