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08 Mar 2012, 22:04
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A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
55%
(hard)
Question Stats:
61% (02:05) correct
39%
(02:09)
wrong
based on 719
sessions
History
Date
Time
Result
Not Attempted Yet
If x and y are integers such that x < y < 0 what is x - y ?
(1) (x + y)(x - y) = 5
(2) xy = 6
(1) (x + y)(x - y) = 5
(2) xy = 6
How would you do this question?
also is it wrong to make statement 1) (x+y)(x-y)=5 into x^2-y^2=5
and then square root both sides to make x-y=√5 ??
please advise... I know another method of getting it right, but I want to confirm if the above can be mathematically done
also is it wrong to make statement 1) (x+y)(x-y)=5 into x^2-y^2=5
and then square root both sides to make x-y=√5 ??
please advise... I know another method of getting it right, but I want to confirm if the above can be mathematically done
Pure algebraic questions like this one are no longer part of the GMAT Data Sufficiency syllabus.
For relevant Data Sufficiency questions, please check the Data Sufficiency forum:
Data Sufficiency Forum
Data Sufficiency Forum
09 Mar 2012, 01:14
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shawndx
This portion in the above highlighted section is absolutely wrong because (x-y)^2 = x^2 - 2xy + y^2 and you cannot take square root of x^2 - y^2 as x-y.
I'm not solving it, but it is obvious that the answer is C or E.
What is the method you're having in your mind ?
09 Mar 2012, 03:03
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A.) First distribute (x+y)(x-y)=5 to get (x^2)-xy+xy-(y^2)=5.
The -xy and +xy cancel each other out so that you now have (x^2)-(y^2)=5.
The question tells us that both x and y are negative (x<y<0) and are integers. From that point you can easliy determine two squares whose difference is 5. And since the question tells us the absolute value of x>y, then x=-3 and y=-2. Sufficient.
B.) The question tells us that the two variables represent negative integers(x<y<0). B tells us that xy=6, which gives us two differnt pairs of integers for x and y: (-1x-6) and (-2x-3). Insufficient.
Answer A.
The -xy and +xy cancel each other out so that you now have (x^2)-(y^2)=5.
The question tells us that both x and y are negative (x<y<0) and are integers. From that point you can easliy determine two squares whose difference is 5. And since the question tells us the absolute value of x>y, then x=-3 and y=-2. Sufficient.
B.) The question tells us that the two variables represent negative integers(x<y<0). B tells us that xy=6, which gives us two differnt pairs of integers for x and y: (-1x-6) and (-2x-3). Insufficient.
Answer A.
