Is -3x³ < -3?
1) -3x < 3
2) x < 0
IMPORTANT CONCEPT: If we divide both sides of an inequality by a NEGATIVE value, we must REVERSE the direction of the inequality sign.
Target question: Is -3x³ < -3?
This is a great candidate for rephrasing the target question.
Aside: We have a free video with tips on rephrasing the target question: https://www.gmatprepnow.com/module/gmat- ... cy?id=1100
Take
-3x³ < -3 and divide both sides by -3 to get
x³ > 1
NOTE: x³
> 1 ONLY IF x
> 1
Now rephrase the target question as....
REPHRASED target question: Is x > 1?
Statement 1: -3x < 3
Divide both sides by -3 to get: x > -1
There are several values of that satisfy this condition. Here are two:
Case a: x = 2, in which case
x > 1
Case b: x = 0, in which case
x < 1
Since we cannot answer the
REPHRASED target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: x < 0
In other words, x is negative
If x is negative, then we can be
certain that
x is NOT greater than or equal to 1.
Since we can answer the
REPHRASED target question with certainty, statement 2 is SUFFICIENT
Answer =
B
Cheers,
Brent
For even more information on rephrasing the target question, you can read this article I wrote for BTG:
https://www.beatthegmat.com/mba/2014/06/ ... t-question
