equation of perpendicular lines

[emilyf]

I am stuck on a problem because it doesn't give me an x and y equation- just the y. Please help!

Write an equation of the line that passes through point P and is perpendicular to the line with the given equation. P(4,-6), y=-3

 

[Mrspi]

I am stuck on a problem because it doesn't give me an x and y equation- just the y. Please help!

Write an equation of the line that passes through point P and is perpendicular to the line with the given equation. P(4,-6), y=-3

If the equation of a line is in the form y = b, as yours is, what kind of line IS that line?

Your equation is

y = -3

What are some points on the line? Since the equation does not have an "x" in it, apparently it does not matter what the x-coordinate of a point is; as long as the y-coordinate is -3, the point will be on that line. So......here are some possible points on your line: (5, -3), (-2, -3), (0, -3), (-8, -3), (7, -3).

Plot those points and draw a line that contains all of them. What kind of line is it? Now, what kind of line would be PERPENDICULAR to the line you've just drawn?

If you drew a line like that, perpendicular to y = -3, and containing the point (4, -6), what would its equation be? (Hint...since YOUR line has an equation with no x in it, a perpendicular to that line will have an equation with no y in it).

 

[emilyf]

so the answer is x=4?

 

[mmm4444bot]

the answer is x = 4 ?

Yes, this is correct.

A vertical line is perpendicular to a horizontal line, and vice versa.

This case is the only exception to the property that states, "slopes of perpendicular lines are negative reciprocals of each other".

It's an exception because vertical lines have no slope; there's no way to calculate the negative reciprocal of something that doesn't exist.

Cheers ~ Mark

 

[emilyf]

thank you so much! you were a great help!