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Hey ! Unfortunately, I still don't get where that '3' comes from... Just don't see it... Could anyone explain further in more detail?! Would be great! _________________

Re: If 2^x-2^(x-2)=3*2^13 what is the value of x? [#permalink]

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23 Jul 2013, 11:51

Bunuel wrote:

Step by step:

\(2^x(1-\frac{1}{2^{2}})=3*2^{13}\)

\(2^x(\frac{2^2-1}{2^{2}})=3*2^{13}\)

Hey, now its clear where the 3 comes from but how did u get the 2^2 there? Sry, was a long day... I bet its easy as hell but I'm just confused atm.. _________________

Re: If 2^x-2^(x-2)=3*2^13 what is the value of x? [#permalink]

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23 Jul 2013, 12:41

Hey, that I understand... but how did u get the 2^2 onto the fraction again to get 2^2-1/2^2 ? I must miss something very fundamental indeed.. _________________

Re: If 2^x-2^(x-2)=3*2^13 what is the value of x? [#permalink]

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06 Oct 2013, 14:11

Hello Everyone,

While completing the GMAT prep exam I stumbled upon a problem solving question that am not able to crack and I am seeking for some advice/pointers on this question:

If 2^x - 2^x-2 = 3(2^13) what is x?

It would be easier to solve if the 3 was not included in the equation at all but of course nothing about the gmat is easy.

Am not looking for the answer just pointers. I did review the exponent rules from the MGMAT Number Properties guide but according to the rule for a * b^ This kind of expression can not be simplified any further so it's kind of confusing,

Re: If 2^x-2^(x-2)=3*2^13 what is the value of x? [#permalink]

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06 Oct 2013, 14:14

Expert's post

dilevbare1 wrote:

Hello Everyone,

While completing the GMAT prep exam I stumbled upon a problem solving question that am not able to crack and I am seeking for some advice/pointers on this question:

If 2^x - 2^x-2 = 3(2^13) what is x?

It would be easier to solve if the 3 was not included in the equation at all but of course nothing about the gmat is easy.

Am not looking for the answer just pointers. I did review the exponent rules from the MGMAT Number Properties guide but according to the rule for a * b^ This kind of expression can not be simplified any further so it's kind of confusing,

Thanks for your help in advance

Merging similar topics. Please refer to the solutions above.

Re: If 2^x-2^(x-2)=3*2^13 what is the value of x? [#permalink]

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26 Feb 2014, 20:31

4

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One more method:

\(2^x - 2^{(x-2)} = 3 * 2^{13}\)

\(2^x - 2^{(x-2)} = ( 4-1 ) * 2^{13}\)

\(2^x - 2^{(x-2)} = 4 * 2^{13} - 1 * 2^{13}\)

\(2^x - 2^{(x-2)} = 2^{15} - 2^{13}\)

Comparing both sides, we get x = 15 = Answer = D

What I like about this method is we need not have to expand/solve the LHS of the equation. Just adjust 3 of the RHS as (4-1) & it does the trick _________________

Kindly press "+1 Kudos" to appreciate

Last edited by PareshGmat on 27 Oct 2014, 21:30, edited 2 times in total.

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