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Positive / Negative

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Positive / Negative

by Thonk02 » Mon Jul 20, 2009 9:25 am
If AX + B = 0, is X>0?

1. A + B > 0

2. A - B > 0


Is there any easier way to do this question other than test numbers? I could not think of any other way to do this problem.



Anwer is E by the way.
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Source: — Data Sufficiency |
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by Sher1 » Mon Jul 20, 2009 10:15 am
ax+b=0

x = -b/a

For x>0 either (a<0 ,b>0) or (a>0,b<0)

Implies that a and b should have opposite signs

1) a + b >0, tells us nothing a and b could both be greater or one can be positive and other can be negative.
INSUFF
2) a - b >0, tells us nothing a and b could both be greater or one can be positive and other negative.
INSUFF

combining both stmts, we still dont know, if a and b have opposite signs for sure.

Therefore E.
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