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