w must be negative
if w is negative the other numbers can be either 1) all (x,y,z) positive or 2) x, y are negative and z is positive. Combining we get z is always positive.
The required is positive and both xz and yz are there, hence we deem x,y are negative and this must be xy
b
word problem
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Source: Beat The GMAT — Problem Solving |
