Source: Official Guide for GMAT Review 2016 Data Sufficiency ; #54

3

# Is zp negative?

Is zp negative?

### 1 Explanation

1

Danny Watts Jr

Statement 1: pz^4 < 0; z^4 will always be a positive number, so p must be negative in order for the solution to be less than 0. However, z itself can be negative or positive, so NOT SUFFICIENT.

Statement 2: p + z^4 = 14. If z = 1 or -1, then p would be positive (13). P would be negative for another result though, so this statement is NOT SUFFICIENT.

Together: P is negative based on statement 1, but neither of the two statements give us a definitive sign for Z. As a result, the statements together or NOT SUFFICIENT, so the answer is (E).

Jan 6, 2018 • Comment

David Recine

Daniel's got it! Statement 1 is insufficient due to number properties-- negative x and positive x will both produce a positive number if raised to an even power.

And for statement 2, it's a matter of testing cases. You can plug in p and z values that get you a negative number for pz or a positive number for pz.