grems Posted May 10, 2008 Share Posted May 10, 2008 If ab is not equal to zero and points (-a,b) and -b,a) are in the same quadrant of the xy plane, is point (-x,y) in the same quadrant? 1) xy>0 2) ax>0 Quote Link to comment Share on other sites More sharing options...
Ankost Posted May 10, 2008 Share Posted May 10, 2008 Sorry, i don't understand how points (-a,b) and (-b,a) can be in the same quadrant. They are in the second and in the 4th qusdrants. Quote Link to comment Share on other sites More sharing options...
saxena_rishu Posted May 11, 2008 Share Posted May 11, 2008 1 and 2 together are required. Option C is the correct answer Quote Link to comment Share on other sites More sharing options...
krovvidy Posted May 11, 2008 Share Posted May 11, 2008 IMO C ... (-a,b) and (-b,a) would be in the same quadrant if ab > 0 i.e., either both a & b are positive or negative (for example, if a=1, b=2 then (-1,2) & (-2,1) are in the same quadrant) (1) INSUFF because we can't say (-x,y) lies in the same quadrant just because x & y are of same sign ... we need to correlate it with a or b ... (2) INSUFF because even if x & a are of the same sign, y & b can be same or different sign ... Taking (1) & (2) it's clear that x & y are of the same sign as 'a' ... hence SUFF Quote Link to comment Share on other sites More sharing options...
Ankost Posted May 12, 2008 Share Posted May 12, 2008 Thank you Krovvidy for your great explanation. Quote Link to comment Share on other sites More sharing options...
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