Question 203228: How do we write the equation of a vertical line? What would be an example?
Answer by PRMath(133)   (Show Source):
You can put this solution on YOUR website! I'm assuming that this question about a vertical line, and the following question about a horizontal line are from the same person. SO I hope that just answering BOTH questions here (instead of answering these separately) will be helpful to you.
Here goes:
HORIZONTAL LINES........
Any time you have an equation of a line in the form of:
f(x) = b
or
y = b
then you have a horizontal line that crosses the y-axis at (0, b).
An example of a horizontal line would be: y = 4 or y = -4.
Essentially, any time you have y equaling something, you have a horizontal line. And... the slope of a horizontal line is 0.
VERTICAL LINES..........
The graph of any equation of the form x = a is a vertical line that crosses the x-axis at (a, 0).
An example of a vertical line would be: x = 4 or x = -4.
Essentially, any time you have x equaling something, you have a vertical line. And, the slope of a vertical line is undefined.
One more thing: A horizontal line has a slope of 0 (as I mentioned) and a vertical line has an undefined slope. Do NOT get the meaning that undefined and 0 are the same. They are NOT, k? Undefined just means that we are agreeing to not give any meaning to the expression of a slope for a vertical line.
I hope this helps you. :-)
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