BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Is \(x \geq 0?\)

Expert replies
Source: — Data Sufficiency |

by Ian Stewart » Thu Jun 27, 2019 7:31 am
Rewriting Statement 1 with zero on one side, x^2 - 9x = 0, so x(x-9) = 0, and x = 0 or x = 9. Either way, x is greater than or equal to zero, so Statement 1 is sufficient.

Statement 2 tells us |x| = -x, which only happens when x is less than or equal to zero (when x is positive, the absolute value doesn't do anything to x, so in that case, |x| = x would be true). Since it's possible that x = 0, in which case the answer to the question is 'yes', and possible that x might be negative and the answer is 'no', Statement 2 is not sufficient, and the answer is A.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

ianstewartgmat.com
Join the discussion