Anyone know how to do this? Is xy > 0 1) x - y > -2 2)

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Anyone know how to do this? Is xy > 0 1) x - y > -2 2) [#permalink]

03 Aug 2006, 17:58

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Anyone know how to do this?

Is xy > 0

1) x - y > -2
2) x - 2y < -6

I think its E, but the OA is C.

Please help.

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Re: xy > 0 DS GMATPREP [#permalink]

03 Aug 2006, 18:20

I am not too good with ineq. But will give it a shot

x,y ={ I, +, - , ==, 0, +1/2, -1/2, +- sqrt(2)}

1) x - y > -2
x=2, y=0
xy = 0 Insuff

x=2, y= -1,
xy<0 Suff
BCE

2) x - 2y < -6
x= 2, y =5
xy> 0

x= -2, y= 6
xy<0
CE

(1) & (2)
(1) x - y > -2
Multiply (2) with -ve
(2) -x +2y>6
Now (1) + (2) since ineq facing in the same direction gives
y> 4
Rewrite (1) x > y-2 --> x>2 since y>4
since x> 2 & y> 4 --> xy > 0

Hence C

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[#permalink]

03 Aug 2006, 20:31

C

St1: Clearly INSUFF

St2: Clearly INSUFF

Combined:

x-y > -2
x-2y < -6 i.e 2y-x > 6
adding these two equations we get
y > 4 substituting thi sin first equation we get x>2. Hence xy > 8: SUFF
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[#permalink]

03 Aug 2006, 23:10

C

1) clearly Insuff
2) Again Insuff

Together

x-y > -2
and
x-2y < -6
or 2y-x > 6
hence y > 4
hence x > 0
therefore xy > 0

[#permalink] 03 Aug 2006, 23:10

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Anyone know how to do this? Is xy > 0 1) x - y > -2 2)

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Anyone know how to do this? Is xy > 0 1) x - y > -2 2)

Anyone know how to do this? Is xy > 0 1) x - y > -2 2)

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