# Thread: Perpendicular to - x=4

1. ## Perpendicular to - x=4

My assignment is to write the equation of the line that is perpendicular to x=4 and passes thru the point (-1, -3). i know how to use the formulas slope intercept and point slope but I do not understand the line x=4. I know( i think) it is parallel to the Y axis. I am confused as to what the slope is. Should I substitute a Value for Y that would be on the line? Then solve for the slope. How do you define the slope of a vertical and horizontal Line. Hope that is not too many questions.

Thanks
Pete

2. Originally Posted by pputthoff
I do not understand the line x=4. I know( i think) it is parallel to the Y axis. I am confused as to what the slope is.
For a discussion of the slope values for vertical lines, try here.

Then note that, to be perpendicular to a vertical line, the second line must be horizontal, and use what you know about the slopes of horizontal lines.

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