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Logitech DS Set 1

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Source: — Data Sufficiency |

by dmateer25 » Thu Dec 18, 2008 2:52 pm
From the question we know that (-a,b) and (-b,a) are in the same quadrant.

Both a and b must have the same sign to be in the same quadrant.

If a=1 and b=1 they would be in quadrant II
If a=-1 and b=-1 they would be in quadrant IV


(1) xy>0

From 1 we know that x and y have the same sign. This doesn't provide enough information to solve.

Insuff

(2) ax>0

From 2 we know that a and x have the same sign. Also, b will have the same sign because we know a and b have the same sign. However, we don't know if y has the same sign.

Insuff

Together we know that a, b, x, and y all have the same sign. Therefore, (-x,y) will be in the same quadrant as (-a,b) and (-b,a).

If they are all positives they will be in quadrant II. If they are all negatives they will be in quadrant IV.

I choose C.
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by logitech » Thu Dec 18, 2008 3:03 pm
@dmateer25
From the question we know that (-a,b) and (-b,a) are in the same quadrant.

Both a and b must have the same sign to be in the same quadrant.

If a=1 and b=1 they would be in quadrant II
If a=-1 and b=-1 they would be in quadrant IV
Great grasp of the knowledge!



Together we know that a, b, x, and y all have the same sign. Therefore, (-x,y) will be in the same quadrant as (-a,b) and (-b,a).

If they are all positives they will be in quadrant II. If they are all negatives they will be in quadrant IV.
Great ending!
I choose C.
And the OA is C
LGTCH
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