SergeNew wrote:

What is the value of x^2-y^2?

(1) x+y=0

(2) x-y=2 .

We need to determine the value of x^2 - y^2. Notice that x^2 - y^2 = (x + y)(x - y).

Statement One Alone:

x + y = 0

Since x + y = 0, regardless of the value of x - y, we have x^2 - y^2 = (x + y)(x - y) = (0)(x - y) = 0. Statement one alone is sufficient to answer the question.

Statement Two Alone:

x - y = 2

We do not have enough information to determine a definitive value for x^2 - y^2. For example, if x = 4 and y = 2, then x^2 - y^2 = 16 - 4 = 12; however, if x = 3 and y = 1, then x^2 - y^2 = 9 - 1 = 8. Statement two alone is not sufficient to answer the question.

Answer: A

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