Expert: Richard J. Raridon - 6/27/2007

Question
QUESTION: Why are equations of horizontal lines of the form y=k, where k is a constant? and why are equations of vertical lines of the form x=k, where k is a constant?


ANSWER: It should be obvious that horizontal lines do not contain x since x can be any value.  For example, if you have the line y=3, then two points on that line are (-10,3) and
15,3) and you can add as many more points as you wish.  Similar for vertical lines where y can have any value.

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QUESTION: I am sorry that I do not understand and do not see the obvious. Still do not understand why equations of horizontal lines of the form y=k where k is a constant and vice versa for x =k being vertical.

Answer
Take a piece of graph paper, put x and y coordinates on it and draw the lines y=3 and x=2 completely across your graph paper.  You should be able to see that y=3 has an infinite number of x values and x=2 has an infinite number of y values.

I'm sorry you felt that I was not polite.  However, I felt that I had explained it clearly the first time.  Did you finally get it?