Data Sufficiency

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

1) x-y = y+2

2) x-y = 1/(x+y)

Recognize the quadratic tested: x^2 - y^2 = (x-y)(x+y). Rephrase: what is (x-y)(x+y)?. Statement (1) is not sufficient (just plug in different values for x,y and test) but (2) is sufficient since multiplying both sides by (x+y) gives us the value we need.

The answer is B. I go through the question in detail in the full solution below (taken from the GMATFix App).



-Patrick

To find: x^2 - y^2 or (x+y)(x-y)

Statement 1:
x - y = y + 2
INSUFFICIENT

Statement 2:
(x-y) = 1/(x+y)
(x-y)(x+y) = 1
SUFFICIENT

[spoiler]{B}[/spoiler]