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Source: — Data Sufficiency |
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by ajith » Sun Feb 14, 2010 11:04 pm
apoorva.srivastva wrote:If x is negative, is x < -3 ?

(1) x^2 > 9
(2) x^3 < -9

OA is A

From st1 we get two cases X >3 and X < -3 ...so is this sufficient to answer conclusively that X< -3???
1) x^2-9>0

(x-3)(x+3)>0

x<-3 or x>3

In the case of X >3 ; x is positive, in the question it is given that x is negative

so the only possibility is x<-3, and it is sufficient to answer whether x<-3

2) Not sufficient

A
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by gmatmachoman » Mon Feb 15, 2010 12:07 am
To negate st 2,

take a value X= -2.2,

X^3=-10.648

-10.648<-9

But -2.2 is not less than -3.

So B alone wont be sufficient.

A is sufficient .

Let X=-4

X^2 = 16 >9

and
-4<-3

Our examples follows st1 and answers whether X<-3

So A
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