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What is the value of x^2 - y^2? (1) x + y = 0 (2) x - y = 2
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02 Jan 2011, 14:08
02 Jan 2011, 14:08
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A
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Difficulty:
15%
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Question Stats:
76% (00:39) correct
24%
(00:46)
wrong
based on 314
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Re: What is the value of x^2 - y^2? (1) x + y = 0 (2) x - y = 2
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02 Jan 2011, 14:22
02 Jan 2011, 14:22
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SergeNew
Hello Folks,
This question is from the review published in 2010. Could anyone please explain to me why the correct answer is A instead of D?
What is the value of x^2-y^2?
1) x+y=0
2) x-y=2
A) Statement (1) Alone is Sufficient but Statement (2) Alone is not sufficient.
D) Each statement Alone is sufficient.
Thank you so much and Happy new decade to everyone.
Serge.
This question is from the review published in 2010. Could anyone please explain to me why the correct answer is A instead of D?
What is the value of x^2-y^2?
1) x+y=0
2) x-y=2
A) Statement (1) Alone is Sufficient but Statement (2) Alone is not sufficient.
D) Each statement Alone is sufficient.
Thank you so much and Happy new decade to everyone.
Serge.
Welcome to Gmat Club Serge!
What is the value of x^2-y^2?
Question: \(x^2-y^2=(x-y)*(x+y)=?\)
(1) x+y=0 --> as one of the multiples is zero then \((x-y)*(x+y)\) must equal to zero. Sufficient.
(2) x-y=2 --> we can not get a single numerical value of x^2-y^2 from this statement. For example: if \(x=2\) and \(y=0\) then the answer will be 4 but if \(x=1\) and \(y=-1\) then the answer will be 0. Not sufficient.
Answer: A.
Hope it's clear.
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Re: What is the value of x^2 - y^2? (1) x + y = 0 (2) x - y = 2
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12 Nov 2017, 08:40
12 Nov 2017, 08:40
Expert Reply
SergeNew
What is the value of x^2-y^2?
(1) x+y=0
(2) x-y=2 .
(1) x+y=0
(2) x-y=2 .
We need to determine the value of x^2 - y^2. Notice that x^2 - y^2 = (x + y)(x - y).
Statement One Alone:
x + y = 0
Since x + y = 0, regardless of the value of x - y, we have x^2 - y^2 = (x + y)(x - y) = (0)(x - y) = 0. Statement one alone is sufficient to answer the question.
Statement Two Alone:
x - y = 2
We do not have enough information to determine a definitive value for x^2 - y^2. For example, if x = 4 and y = 2, then x^2 - y^2 = 16 - 4 = 12; however, if x = 3 and y = 1, then x^2 - y^2 = 9 - 1 = 8. Statement two alone is not sufficient to answer the question.
Answer: A
