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Is ixyl>lxllyl ? 1)y<x 2)x*y<0 [#permalink]
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04 May 2006, 16:31
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Is ixyl>lxllyl ?
1)y<x
2)x*y<0



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Re: DS absolute value [#permalink]
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04 May 2006, 18:00
Natalya Khimich wrote: Is lxyl > lxl  lyl ? 1) y<x 2) x*y<0
from i, x>y means x or y, both, could be +ve or ve. if x and y both are +ve, lxyl = lxl  lyl otherwise not.
from ii, either x or y is +ve and the other one is ve. so suff because no matter the value of each, lxyl is always greater than lxl  lyl.
SO B.



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St1: y<x
If x = 3, y = 2, then xy = 5, x  y = 1 xy > x  y
If x = 2, y = 1, then xy = 1, xy = 1 xy = xy
Insufficient.
St2: xy < 0
Means either:
(x,y) = (negative, positive) or (positve, negative), or (fraction, fraction)
If x = 3, y = 10, xy=7, xy=7 ; xy>xy
If x = 10,y = 3, xy = 7, xy=7 ; xy > xy
Insufficient.
Using St1 and St2:
If x = 3, y = 10, xy=7, xy=7 ; xy>xy
If x = 100, y = 10, xy = 110, xy=90; xy >xy
If x = 3, y = 7, xy10, xy=4; xy > xy
If x = 1/2, y = 1/4, xy = 1/2, xy = 1/2
Insufficient.
Ans E



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ywilfred wrote: St2: xy < 0 Means either:
(x,y) = (negative, positive) or (positve, negative), or (fraction, fraction)
If x = 3, y = 10, xy=7, xy=7 ; xy>xy If x = 10,y = 3, xy = 7, xy=7 ; xy > xy Insufficient.
x and y both cann't be ves or +ves.



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B it is, though it is tempting to mark C at first glance.



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Professor wrote: ywilfred wrote: St2: xy < 0 Means either:
(x,y) = (negative, positive) or (positve, negative), or (fraction, fraction)
If x = 3, y = 10, xy=7, xy=7 ; xy>xy If x = 10,y = 3, xy = 7, xy=7 ; xy > xy Insufficient. x and y both cann't be ves or +ves.
ah yes !! that was a bad mistake. thanks for pointing it out.



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Re: DS absolute value [#permalink]
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11 Jun 2006, 14:50
Professor wrote: Natalya Khimich wrote: Is lxyl > lxl  lyl ? 1) y<x 2) x*y<0 from i, x>y means x or y, both, could be +ve or ve. if x and y both are +ve, lxyl = lxl  lyl otherwise not. from ii, either x or y is +ve and the other one is ve. so suff because no matter the value of each, lxyl is always greater than lxl  lyl. SO B.
so if both x and y are negative would "lxyl = lxl  lyl" be true?
thanks




Re: DS absolute value
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11 Jun 2006, 14:50






