Q. If x != -y, is x-y/x+y > 1 ?
x-y/x+y > 1
x-y > x+y
2y < 0 --> y<0
So the question is -- is y < 0 ?
and (2) is y < 0....
So is (2) not sufficient? Shouldn't the answer be B?
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Ian Stewart
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Your mistake is in the line above: you don't know whether x+y is negative. If x+y is negative, when you multiply both sides by x+y, you'd need to reverse the inequality.rseeker2 wrote: x-y/x+y > 1
x-y > x+y
This is probably the most common trap in GMAT inequality questions. If you are ever tempted to multiply or divide on both sides of an inequality by an unknown, *always* ask yourself: do I know the sign of this unknown? If you don't know whether the unknown is positive or negative, you can't multiply or divide by it, since you won't know what direction the inequality should face afterwards.
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dario.brignone
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As we don't know the sign of the variables we cannot divide/multiply.
But can we do this?:
(X-Y-X-Y)/(X+Y) > 0
-2Y/(X+Y) > 0
Thanks.
But can we do this?:
(X-Y-X-Y)/(X+Y) > 0
-2Y/(X+Y) > 0
Thanks.
