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Co-ordinate geometry

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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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.

Thanks
You can, for example never foretell what any one man will do, but you can say with precision what an average number will be up to!
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Source: — Quantitative Reasoning |

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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