Is (4^-x)(y�) > 0?
1) xy < 0
2) y^x < 0
Here's my solution:
Target question: Is (4^-x)(y�) > 0?
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
First recognize that (4^-x) IS POSITIVE for ANY value of x. So, (4^-x) =
some positive number.
In other words, (
4^-x)(y�) = (
some positive number)(y�)
What can we conclude about y�? Well, y� is always greater than
or equal to zero.
In fact, the ONLY time y� is NOT greater than zero is when
y = 0.
So, the ONLY time that (
4^-x)(y�) is NOT greater than zero, is when
y = 0.
In other words, if y has a non-zero value, (4^-x)(y�) > 0.
We can now REPHRASE the target question as follows....
REPHRASED target question: Does y have a non-zero value?
At this point, it's relatively easy to check the statements.
Statement 1: xy < 0
This means that xy ≠0, which means that y ≠0.
In other words, we can be certain that
y has a non-zero value.
Since we can answer the
REPHRASED target question with certainty, statement 1 is SUFFICIENT
Statement 2: y^x < 0
If y^x < 0, then we know that y ≠0.
In other words, we can be certain that
y has a non-zero value.
Since we can answer the
REPHRASED target question with certainty, statement 2 is SUFFICIENT
Answer =
D
Cheers,
Brent
