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Slope or No Slope!?!?!?

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Slope or No Slope!?!?!?

by smclean23 » Thu Aug 07, 2008 7:01 pm
. Is line L parallel to the y-axis?

(1) The equation of line L is x = 4.
(2) The points (4. 2) and (4, - 5) are on line L .


Obviously 1 is sufficient...but 2 is where I got stumped. The way I attacked this was to find the slope of these two. I end up getting -3/0. I immediately stopped and determined that 2 wasn't sufficient, but is there a 0 slope?

Answer is D.
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by amitansu » Fri Aug 08, 2008 12:16 am
The slope of vertical line is undefined. (-3/0 is infinite not zero)
So, if the slope is undefined the line has to be vertical hence parallel to y -axis.


Amit
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by pepeprepa » Fri Aug 08, 2008 12:51 am
You can solve it as you did by calculating the slope.
Your -3/0 slope means the line is parallel to y-axis as 0/-1 means the line is parallel to x-axis.

Try to see it on a graph instead of maths, I think it is simpler.
Axis-y is in red, you have your two points required to draw a line, it is obvious the line is parallel with a graph!
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