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Source: — Data Sufficiency |
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by Jim@StratusPrep » Tue Jun 05, 2012 9:15 am
1) because they are not integers there are infinite combinations
2) there are infinite combinations of integers

The only two together are below:

X,Y could be 7, 1 , which is 6^4
X,Y could be -7,-1, which is (-6)^4

Both of these give you the same answer

C
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by Anurag@Gurome » Tue Jun 05, 2012 8:25 pm
alex.gellatly wrote:What is the value of [x-y]^4?

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

Thanks
(1) xy = 7
If x = 1, y = 7, then (x - y)^4 = (1 - 7)^4 = (-6)^4
If x = 1/7, y = 7, then (x - y)^4 = (1/7 - 7)^4 = fraction
No definite answer; NOT sufficient.

(2) x and y are integers.
There can be infinite values of (x - y)^4; clearly NOT sufficient.

Combining (1) and (2), we know that xy = 7, such that x and y are integers.
Possible combinations are: (x = 1, y = 7), (x = 7, y = 1), (x = -1, y = -7), (x = -7, y = -1)
All these combinations give the same value for (x - y)^4 as (6)^4 or (-6)^4, which gives the same value; SUFFICIENT.

The correct answer is C.
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