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what sine is W?

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tomslawsky
 Post subject: what sine is W?
 Post Posted: Fri Jun 10, 2011 9:48 pm 
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Students


Posts: 138
What sign is W?

1) W^3(1-W^2)<0
2) W^2 - 1<0

The correct answer should be C, but I'm not 100% sure because this problem was only inspired by an OG problem, and not taken directly.

Please help with a "simple" solution. Thanks
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george.kourdin
 Post subject: Re: what sine is W?
 Post Posted: Sat Jun 11, 2011 3:12 pm 
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Course Students


Posts: 98
think it is C

a) insufficient
if w = 2 then (a) < 0
if w = -1/4 then (a) < 0

b) w has to be < 1 for be to be true however since its w^2 w can be either -1/2 or 1/2 so b is insufficient

combine (a) and (b) and we know that w < 1. for (a) to be < 0
w^3 must be < 0 and 1-w^2 must be > 0 so -1<w<0
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jnelson0612
 Post subject: Re: what sine is W?
 Post Posted: Sun Jun 12, 2011 10:54 pm 
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ManhattanGMAT Staff


Posts: 1857
Great work George!

_________________
Jamie Nelson
ManhattanGMAT Instructor
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