(-a , b) and (-b , a) are the 2 points in a same quadrant and product ab not equal to zero.
Is a point (-x , y) in the same quadrant?
a. xy > 0
b. ax > 0
Answer C - a and b together sufficient
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testprepDublin
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If (-a , b) and (-b , a) are in the same quadrant and if a a & b are non-zero then a and b must have the same sign. As -a is in the same quadrant as -b and a is in the same quadrant as b.
So if (-x,y) is to be same quadrant x and y must have the same sign as each other and as a and b.
(1) same as each other
insufficient
(2) x same as a and b
insufficient
(1)&(2) x and y same as a and b
sufficient
So if (-x,y) is to be same quadrant x and y must have the same sign as each other and as a and b.
(1) same as each other
insufficient
(2) x same as a and b
insufficient
(1)&(2) x and y same as a and b
sufficient
Deirdre at testprepdublin.com
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sunilrawat
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My approach,
a. xy>0
either x and y are both positive, or both negative.
(-x,y) could be either in I or II quadrant.
not sufficient.
b. ax>0
'a' being a constant, x>0
no info about y. not sufficient.
combining the two,
x>0 means y>0
(-x,y) lies in the same quadrant.
sufficient.
OA C
a. xy>0
either x and y are both positive, or both negative.
(-x,y) could be either in I or II quadrant.
not sufficient.
b. ax>0
'a' being a constant, x>0
no info about y. not sufficient.
combining the two,
x>0 means y>0
(-x,y) lies in the same quadrant.
sufficient.
OA C
