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Please explain- Equation

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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Source: — Quantitative Reasoning |
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by dominhtri1995 » Sat Oct 26, 2013 9:16 am
you will have
x = sqrt ( 4y(x-y) )

Go check x with the answer. Plug it in the equation, it will be A :D
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by [email protected] » Sat Oct 26, 2013 1:17 pm
Hi shibsriz,

This question has a hidden Classic Quadratic within it.

Start by squaring both sides of the equation:

X^2 = 4XY -4Y^2

Notice how there's a "squared" X term and a "squared" Y term? That's the big clue that you're looking at a quadratic.

X^2 - 4XY + 4Y^2 = 0

Now factor:

(X - 2Y)^2 = 0

X = 2Y

Final Answer: A

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by Mike@Magoosh » Fri Nov 01, 2013 11:47 am
Dear [email protected],
It appears that Rich gave you a good solution to this particular problem.

I would just like to recommend knowing cold three fundamental algebra equations:
https://magoosh.com/gmat/2013/three-alge ... -the-gmat/
These are shortcuts that will help you a lot.

Mike :-)
Magoosh GMAT Instructor
https://gmat.magoosh.com/
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