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DS OG #142

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DS OG #142

by rainbownlife » Fri Mar 28, 2008 9:30 am
if x is an integer, is 9^x + 9^(-x) = b?
1) 3^x + 3(-x) = sqrt(b+2)
2) x > 0 = b


I understand and can solve (1)
However what is 2)
In the explanation OG says that the given info is NOT SUFFICIENT.

Can somenody please explain what this expression means ??

If i assume that expression means
x>0 and b=0 then
9^x + 9^(-x) = 0 ?
Ans is No as power of 9 or 1/9 will always be +ve and expression will never be 0. Hence should be SUFFICIENT.

somebody Please explain the expression and wha it means.

I just dont understand what it means

thanks!
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by rey.fernandez » Sat Mar 29, 2008 10:33 pm
Statement (2) reads:

x > 0

And that's it. You must have misread it?

Because (2) tells us only about x and nothing about b, it must be insufficient given the question.

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by Stuart@KaplanGMAT » Sun Mar 30, 2008 10:31 am
rey.fernandez wrote:Statement (2) reads:

x > 0

And that's it. You must have misread it?

Because (2) tells us only about x and nothing about b, it must be insufficient given the question.

Rey
My version of the OG has:

(2) x > 0 = b

in both the question and the explanation section. However, the actual explanation ignores the info.

I'd just write this off as a really bad question.
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by Kaunteya1 » Sun Mar 30, 2008 10:38 am
My version just says x > 0
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by rainbownlife » Wed Apr 02, 2008 9:21 am
My OG (edition 11) also has x > 0 = b
Its stange, same editions have different information
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by bluetornado » Sat Nov 05, 2011 8:06 am
why can't we do (3^x)^2+(3^-x)^2 = (sqrt(b+2))^2?
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