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Math Help - exponential equations

  1. #1
    Junior Member
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    exponential equations

    help please, i'm not sure how to solve this question. i know i need to use change of base, but i'm still confused.

    solve equation, check for extraneous roots

    2^x + 12(2)^-x = 7
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  2. #2
    MHF Contributor
    Grandad's Avatar
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    Hello extraordinarymachine
    Quote Originally Posted by extraordinarymachine View Post
    help please, i'm not sure how to solve this question. i know i need to use change of base, but i'm still confused.

    solve equation, check for extraneous roots

    2^x + 12(2)^-x = 7
    Multiply both sides by 2^x and re-arrange:
    (2^x)^2-7.2^x+12=0

    \Rightarrow (2^x-3)(2^x-4)=0
    Can you complete it now?

    Grandad
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  3. #3
    Junior Member mrmohamed's Avatar
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    Lightbulb

    Quote Originally Posted by extraordinarymachine View Post
    help please, i'm not sure how to solve this question. i know i need to use change of base, but i'm still confused.

    Quote Originally Posted by extraordinarymachine View Post


    solve equation, check for extraneous roots

    2^x + 12(2)^-x = 7


    Hi all
    Last edited by mrmohamed; December 1st 2009 at 11:02 AM.
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