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02 Jan 2011, 14:08
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A
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Difficulty:
15%
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Question Stats:
76% (00:40) correct
24%
(00:49)
wrong
based on 383
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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
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02 Jan 2011, 14:22
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SergeNew
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.
12 Nov 2017, 08:40
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SergeNew
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
