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# What is the value of (x - y)^4? (1) The product of x and y

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VP
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What is the value of (x - y)^4? (1) The product of x and y [#permalink]  22 Jun 2008, 05:44
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52% (01:31) correct 48% (00:26) wrong based on 19 sessions
What is the value of (x - y)^4?
(1) The product of x and y is 7.
(2) x and y are integers.
Current Student
Joined: 28 Dec 2004
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Location: New York City
Schools: Wharton'11 HBS'12
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Re: DS: value of (x - y)^4 [#permalink]  22 Jun 2008, 06:07
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looks to be C

(x-y)^4?

xy=7..ok, well if x=7 y=1.. you get 6^4..

or you could have x=14 y=1/2 then 13.5^4..isnuff

2) is clearly insuff

together..

xy=7..x and y integers..we know 7 is a prime..so x=7 y=1 or y=7 x=1..either way ans is 6^4

C it is.
Manager
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Re: DS: value of (x - y)^4 [#permalink]  22 Jun 2008, 06:11
ritula wrote:
What is the value of (x - y)^4?
(1) The product of x and y is 7.
(2) x and y are integers.

Should be C. If x and y are integers and the product of x and y is 7 then we can determine the value of x and y...which is either 1 and 7 or 7 and 1. Both cases generate same value of (x-y)^4, which is 6^4.
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Re: DS: value of (x - y)^4 [#permalink]  22 Jun 2008, 10:20
The key is that product is a prime number...makes our life easier...Only way to have a product 7 is x=7, y=1 or x=1, y = 7 when both are integers...

Also, an even power for x-y makes it a C....for any off power of x-y, this would have been E, as you will get a positive and a negative solution...
VP
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Re: DS: value of (x - y)^4 [#permalink]  22 Jun 2008, 22:25
yes OA is C indeed. thanks !
SVP
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Re: DS: value of (x - y)^4 [#permalink]  22 Jun 2008, 23:06
Also do not ignore the fact that x and y can be negative (-1 and -7 or -7 and -1). In either case, the answer will be C.
Manager
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Re: DS: value of (x - y)^4 [#permalink]  09 Dec 2009, 08:40
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Statement 1 ---------------Insufficient

X can be 7 when Y is 1 or X can be 1/7 when Y is 7 and so on……

Multiple answers, hence insufficient

Statement 2 --------------CLEARLY INSUFFICIENT (No info about the numbers)

Combining the two,

Since they are both integers and 7 happens to be a prime number divisible by 1 and 7 only, the numbers are 7 and 1

Whether y is 7 or 1 (Same with x), does not matter as the power (4 in this case) is even which will give the same positive result
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Re: DS: value of (x - y)^4 [#permalink]  18 Sep 2011, 02:32
i have to say nice question..totally deceive me....
Manager
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Re: DS: value of (x - y)^4 [#permalink]  18 Sep 2011, 20:15
Looks like a straight C.

Re: DS: value of (x - y)^4   [#permalink] 18 Sep 2011, 20:15
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# What is the value of (x - y)^4? (1) The product of x and y

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