Is x 0? (1) -2x 0 (2) x^3

Question

Is x > 0?

(1) -2x > 0

(2) x^3 < 0

BrentGMATPrepNow · Accepted Answer

Target question : Is x > 0? Statement 1 : -2x > 0 Divide both sides by -2 to get: x < 0 (we reverse the inequality symbol because we divided by a NEGATIVE value) If x < 0, then the answer to our target question is NO, it is not the case that x > 0 Since we can answer the target question with certainty, statement 1 is SUFFICIENT Statement 2 : x³< 0 There are a few ways to handle this. Here's one approach. Since x³< 0, we can be certain that x ≠ 0, which also means that x² is POSITIVE If x² is POSITIVE, we can take x³< 0 and divide both sides by x² to get: x < 0 If x < 0, then the answer to our target question is NO, it is not the case that x > 0 Since we can answer the target question with certainty, statement 2 is SUFFICIENT Answer: D RELATED VIDEO https://www.youtube.com/watch?v=Od98BOicIq4

vmelgargalan · Answer

I am confused as to why the answer is D. Because for option 2 x could be positive or negative. So we can't be sure whether x is larger or smaller than 0

Bunuel · Answer

How does positive value satisfy x^3 < 0? (positive)^3 > 0 and (negative)^3 < 0.

vmelgargalan · Answer

Yep, you are right. Had a brain fart. It doesn't. Silly, that this was the only wrong question I got... Once again I read the question too fast and I thought both signs were in the same direction.

bumpbot · Answer

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Is x > 0? (1) -2x > 0 (2) x^3 < 0

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