Lesson: FOIL Method for Expanding

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For the last ques from Math Rev...

Is x^2 > y^2?

(1) x + y = 2
(2) x > y


How is the OA C? my explanation:

-Assume 1 and 2 are not suff on their own
-1+2)
x= 2, y= 0 (satisfying 1 and 2) --> Yes, 4 > 0
x= 2, y= -4 (satisfying 1 and 2) --> No, 4 is not greater than 16

Shouldn't the answer be E???
gmat-admin's picture

x= 2, y= -4 does not satisfy statement 1

Brent, since statement 2 clearly states that, X>Y, it should be true for x^2>y^2 or even x^3>y^3, Right? Going by this logic, clearly, Statement two alone is sufficient?
gmat-admin's picture

"...since statement 2 clearly states that x > y, it should be true for x^2 > y^2..."

That's not true. Here's a counter-example:

x = -3 and y = 1
Here, x < y, but it is NOT the case that x² < y².
If x = -3, then x² = (-3)² = 9
If y = 1, then y² = (1)² = 1
So, x² is greater than y²

Cheers,
Brent

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