GMAT Prep?? (Coordinate Geo) Pract2

dferm

If ab does not = 0 and points (-a,b) and (-b,a) are in the same quadrant of the xy-plane, is point (-x,y) in this same quadrant?

(1) xy >0
(2) ax >0

Please Help..

thanks...

amitansu · Posted: Wed May 14, 2008 1:10 am Post subject:

Is the ans E here ?

rdadbhawala · Posted: Wed May 14, 2008 2:59 am Post subject: Answer is C

From the question stem itself, since (-a, b) and (-b, a) are in the same quadrant, we can say that -a, -b are the same sign (+ve or -ve) and similarly, a,b are the same sign.

From stmt (1) we know that both X, Y > 0 or both X, Y < 0. (i.e. both are having tehe same sign.) But we don't know the relation of X or Y with A or B. Thus stmt 1 is not sufficient.

From stmt (2) we know that both X, A > 0 or both X, A < 0. But this does not give us the relation of X with Y. (That is given only in option 1, not in the question stem).

Putting both stmts together with the question stem, we know that A and B are the same sign, X and Y are the same sign, and A and X are the same sign. This is sufficient to say that (-x,y) is in the same quadrant as (-a,b).

- RD