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DS Sum of Squares Question

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Source: — Data Sufficiency |

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Re: DS Sum of Squares Question

by Brent@GMATPrepNow » Sun Sep 20, 2009 10:20 am
ogbeni wrote:Can you explain your reasoning? The correct answer is A. I went for E - bummer :(

What are the values of X and Y
1. X^2 + Y^2=0
2. X^2 - Y^2=0
(1) We know that x^2 must always be either positive or equal to zero. So, if x^2 + y^2 = 0, then neither x^2 nor y^2 can be a positive number, since the sum of the squares could never be zero. The ONLY way for x^2 + y^2 to equal zero, is for x^2 to equal zero and y^2 to equal zero. This means that both x and y must equal zero.

(2) Lots of possibilities here. INSUFFICIENT.
Brent Hanneson - Creator of GMATPrepNow.com
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by glorydefined » Sun Sep 20, 2009 11:10 am
this is unbelievable...how can even GMAC think like this...I chose c...and fell into the trap :shock:
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by ogbeni » Sun Sep 20, 2009 11:32 am
Brent,

Great explanation - thanks! I'm knocking myself on the head for not seeing things the way you've explained them. Lesson learned!! Yaay
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