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# What is the value of (x-y)^4 (1) The product of x and y is 7

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What is the value of (x-y)^4 (1) The product of x and y is 7 [#permalink]

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09 Aug 2005, 11:34
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What is the value of (x-y)^4

(1) The product of x and y is 7
(2) x and y are integers

Kudos [?]: 168 [0], given: 0

Senior Manager
Joined: 30 May 2005
Posts: 275

Kudos [?]: 44 [0], given: 0

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09 Aug 2005, 12:54
vivek123 wrote:
What is the value of (x-y)^4

(1) The product of x and y is 7
(2) x and y are integers

not sure i would say c

not sure

st 1 x*y=7
Many ways a product can gives 7
7*1
4/3*7/4

INS to find value of x and y

st2 x and y integers many choices possibles insufficient

together
we know both x and y are integer
since 7 IS a prime
x*y =7*1
plz correct me if i am wrong
what 's the OA?
THANKS

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Senior Manager
Joined: 04 May 2005
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Location: CA, USA

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09 Aug 2005, 20:49
C

from 1) and 2) the two numbers have to be
-1, -7 or 1 , 7

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SVP
Joined: 03 Jan 2005
Posts: 2231

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09 Aug 2005, 21:03
vivek123 wrote:
What is the value of (x-y)^4

(1) The product of x and y is 7
(2) x and y are integers

(x-y)^4=(x^2+y^2-2xy)^2
To know its value it will not be sufficient to know xy=7 or to know that both x and y are integers.

Combined we know that x and y can only be (1,7) or (-1,-7). (The order is not important.) The quadratic terms make the negative signs go away so the value of (x-y)^4 would be unique.

I agree with C.
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Re: DS: Algebra   [#permalink] 09 Aug 2005, 21:03
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