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Co-ordinate geometry

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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Co-ordinate geometry

by vinay1983 » Thu Oct 10, 2013 10:47 pm
Slope = rise/run = is it (y1-y2)/(x1-x2) or (y2-y1)/(x2-x1)? does it change anything?

For distance between points formula √(x1-x2)+(y1-y2) or √(x2-x1)+(y2-y1). Does the oder matter here similar to my above question.

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by Mike@Magoosh » Fri Oct 11, 2013 10:36 am
vinay1983 wrote:Slope = rise/run = is it (y1-y2)/(x1-x2) or (y2-y1)/(x2-x1)? does it change anything?

For distance between points formula √(x1-x2)+(y1-y2) or √(x2-x1)+(y2-y1). Does the oder matter here similar to my above question.

Thanks
Dear vinay1983,
I'm happy to help. :-)

Here's a blog about slope:
https://magoosh.com/gmat/2012/gmat-math- ... x-y-plane/
First of all, in the slope equations you quoted, it doesn't matter. (4-3)/(8-7) = (3-4)/(7-8). If you reverse the order of subtraction in both the numerator and the denominator, the value of the overall fraction remains unchanged.
Actually, I would recommend just using the idea slope - rise/run, and thinking about it visually, rather than relying exclusively on a very algebraic formula.

For distance, I think memorizing that formula is a unholy abomination. Here's what I recommend instead:
https://magoosh.com/gmat/2012/gmat-coord ... wo-points/

Does all this make sense?
Mike :-)
Magoosh GMAT Instructor
https://gmat.magoosh.com/
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