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by sudhir3127 » Wed Jul 16, 2008 10:56 pm
can u post the question .. i am not being able to see the picture.
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Re: Question Exponents

by parallel_chase » Thu Jul 17, 2008 2:36 am
ajmoney09 wrote:Image

No idea.

I divided by two to end up with 2^x - 2^x-1 = 3^13

Don't know what to do after that....OA is D

Help,
Thanks,
AJ.
2^x - 2^x-2 = 3(2^13)


2^x - 2^x/2^2
2^x(1-1/2^2) => 2^x (3/4)

=> 3(2^x-2) = 3 (2^13)


therefore x =15

Let me know if you have any questions.
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by pepeprepa » Thu Jul 17, 2008 6:04 am
When you have this kind of equation, just factorize the left side by 2^x
You have to know that 2^(-x)=1/(2^x) and it's ok
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by anksanks » Thu Jul 17, 2008 6:44 am
2^x – 2^(x-2) = 3 * (2^13)
=> 2^x (1 – 1 / 2^2) = 3 * (2^13)
=> 2^x (3/4) = 3 * (2^13)
=> 2^x = 4 * (2^13) = 2^2 * (2^13) = 2^(13+2)=2^15
=> 2^x=2^15
=>x = 15
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