I am noticing that I am having trouble with certain type of algebra questions and am not sure how to tackle them.

For example:

If ab doesnt equal 0 and (-a,b) and (-b,a) are in the same quadrant, is (x,y) in the same quad?

1. xy>0
2.ax>0

OR

is y< (x+z)/2?

1. y-x < z-y
2. z-y > (z-x)/2

Is seems like anything without specifc values I can't figure out how to solve. I have tried picking values but I am still getting these questions wrong. What should I do?

Please provide the Veritas text, page, and problem numbers for these.

Thanks.

- Veritas Help

They were from a gmat prep test. I just want to know the best way to approach those type of questions.