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DS on squares

by knight247 » Tue Aug 23, 2011 10:48 am
Is x>0?
(1)x²>36
(2)x^4>16

Don't have an OA.
(1)Assume x²=64 Hence x=±8 INSUFFICIENT
(2)Assume x^4=81 x=±3 INSUFFICIENT

Combining both we still can't get a resolution. Hence E. Is my logic correct?

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by vinod192 » Tue Aug 23, 2011 11:32 am
1. Insufficient as X having 2 values +6/-6
2. Sufficient as X>2 since 2>0 hence X>0

Answer is B.

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by HeintzC2 » Tue Aug 23, 2011 12:08 pm
x = -2 also yields a result of 16 (-2*-2*-2*-2). Therefore, x >2 or x<-2 from statement 2.
combining these statements yields no useful new data (statement 1 told us x>6 or x<-6).

IMO E
vinod192 wrote:1. Insufficient as X having 2 values +6/-6
2. Sufficient as X>2 since 2>0 hence X>0

Answer is B.

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by BlindVision » Tue Aug 23, 2011 12:16 pm
knight247 wrote:Is x>0?
(1)x²>36
(2)x^4>16

Don't have an OA.
(1)Assume x²=64 Hence x=±8 INSUFFICIENT
(2)Assume x^4=81 x=±3 INSUFFICIENT

Combining both we still can't get a resolution. Hence E. Is my logic correct?
E
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by GmatKiss » Wed Aug 24, 2011 1:00 am
IMO: E
(1)x²>36
x < -6 and x > 6
(2)x^4>16
x > -2 and x < 2

1+2, still not certain on the x! Hence E

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by navami » Thu Aug 25, 2011 4:41 am
Clearly E.

hence according to Option 1. x <-6 or x >6
according to option 2. x<-2 or x >2

even if we combine 1 AND 2
x could be -7 or 7

hence E
This time no looking back!!!
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