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GMAT Prep is 1/k > 0

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Source: — Data Sufficiency |
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by amitansu » Mon May 12, 2008 7:00 am
This prob is already discussed.

However,

From 1: 1/k-1 > 0 says : both numerator and denominator are positive.

So K-1 >0 => k>1 and from q we know k only could be 2 onwards so 1/K would be always greater than 0.

Sufficient.
From 2 : 1/k+1 >0 says : k+1 >0 here we can't limit K's value.
For example; K could be -1/2 then 1/k <0>0 so insufficient.
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answer

by adam15 » Tue May 13, 2008 10:21 am
the question is bite difficult,
*if k is assumed to be different from 0 because of 1/k,
*if K is assumed to be different from -1 because of deminator on k+1
*the same for k-1.
to begin with statement small changes are needed:
(1)to say that 1/k-1>0 is the same as k+1>0, then k>1
(2)to say that 1/k+1>0 is the same as k-1>0, then k>-1

1 is not enough ssince k can be negative or positive.
2 is sufficient since k is all the time is postive and the answer follow, then A is the right answer.
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