Value of (x-y)^4

[sq720]

What is the value of (x-y)^4
A.) the product of x and y is 7
B.) x and y are integers

[yogami]

IMO E

(1) tell sus that xy is 4. But if you expand (x - y)^4 it would give powers of x and y independently which cannot be solved as x and y can be anything, integers or decimalshence insuff
(2) tells us that x and y are integers. But does not give any values so insuff

combining we get x and y values to be either 1 and 7 or -1 and 0-7 and in either cases give the value so suff

[prax_us]

The answer is C.
1. The product of X & Y is 7. Not sufficient. As X=0.01, Y=700 or X=0.1, Y=70 producing different results for (X-Y)^4
2. X & Y are integers; Not sufficient to arrive at single results for (X-Y)^4.

Combinging both -
XY = 7
=> X = 1, Y =7
=> X = -1, Y = -7
=> X = 7, Y = 1
=> X = -7, Y = -1
All result into 6^4.
Thus answer is C.

[vinayakdl]

IMO :C



Vinayak

[ogbeni]

I'm kinda confused

How does (1-7)^4 = (-1-7)^4?

The answer should be E because combining both statements does not give one value for (x-y)^4. Please show me what I'm missing.

[raghavsarathy]

I'm kinda confused

How does (1-7)^4 = (-1-7)^4?

The answer should be E because combining both statements does not give one value for (x-y)^4. Please show me what I'm missing.

When both are negative , (-1 - (-7) )^4 which is 6^4


So we get the same value

[ogbeni]

OMG you are so right!! Little mistakes such as mine could lower your score. Note taken! Thanks!!