Posted by Patricia on Friday, April 11, 2008 at 11:53pm.
Why is the line x=4 a vertical line?

Algebra  Anonymous, Saturday, April 12, 2008 at 12:08am
Hi:
The equation x=4 refers to all ordered pairs whose x value is 4. Thus, for example, (4,o), (4,1), (4,2), etc. all satisfy the given equation. Notice that the three ordered pairs above fall on the vertical line passing through 4 on the xaxis. Indeed, all ordered pairs on such vertical line have x coordinate =4.
Regards,
Rich B. 
Algebra  Patricia, Saturday, April 12, 2008 at 12:14am
Thanks a million!