If xy != 0, is x

Question

If xy != 0, is x < y,

1 - x^4 < y^4
2.- x^-3 < Y^-3.

Thanks.

crackgmat3 · Answer

B.

Is x<y ?

1) Insufficient
x can be +2 or -2 and y can be +3 or -3

2) Sufficient
if x^-3 < y^-3, then x will be greater than y.

Alex_NL · Answer

Ok,

I am doing too much work now because I am not sure if it is x^4 or -x^4.
The same at the second statement.

and xy! = 0....could someone clarify that to me.

Maybe I am really dumb, but I have no clue.

Thanks.

Regards,

Alex

anuramm · Answer

sorry for the confusion, there is no minus sign.
the two parts read as 
1. x^4 < y^4
2. x^-3 < Y^-3

smandalika · Answer

I think its still B.
this is because with even power the relevance of the sign is lost 
ie. consider -2 ^ 4 = 16 and -3 ^ 4 = 81 and
 2^4 = 16 3^4 =81 
so in the former case x > y and the latter case x<y

but the 2nd condition keeps the sign parity and is sufficient since the power is odd

 (-2)^3 > (-3)^3 => -2 > -3 
and (4)^3 > (3)^3 => 4 > 3

hardworker_indian · Answer

B.

I does not say anything about the sign of Y. It might be negative or positive.
II. X^3>Y^3 =>(X^2)X > (Y^2)Y
X^2 and Y^2 does not have any sign. So X is greater than Y.

Just for discussion, lets call this problem #2, what would be the solution for:
If xy != 0, is x < y?
1. - x^4 < y^4
2. - x^-3 < Y^-3.
(there is minus sign before the x in both statements)

intr3pid · Answer

First things first, if xy! here stands for the factorial of xy, then it can't be true. A factorial is a non-zero number.

Assuming that's a typo, the answer to the original question would be B for the reasons you guys mentioned.

The answer to Problem # 2 will be E. We don't have enough information from the givens to determine the answer.

Alex_NL · Answer

My apologies that I came up with the signs for x and y.
However I mentioned this because I try to calculate problems within certain time limits. This question was not sure for me whether I have to use minus or not.

Back to the question: My answer is B.

Regards,

Alex

anuramm · Answer

The OA is B.

Could anyone explain what is wrong with my reasoning.

Statement 2 says x^-3 y.

Let x = -3 and y =2.

-1/27 < 1/8, but x < y.

So 2 is insufficient.

So answer is E.

Thanks.

If xy != 0, is x < y, 1 - x^4 < y^4 2.- x^-3 <

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards