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Math Help - exponential functions..

  1. #1
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    exponential functions..

    just a quick question, what am I doing wrong here? x = 5/2

    (1/4)^(1-x) = 8


    4^(-1+1-x) = 2^3

    4^(-x) = 2^3

    2^2(-x) = 2^3

    2(-x) = 3

    -x = 3/2

    x = -3/2 ?
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  2. #2
    Member Glaysher's Avatar
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    (1/4)^{1 - x} = 8

    (2^{-2})^{1 - x} = 2^3

    2^{-2 + 2x} = 2^3

    -2 + 2x = 3

    2x = 5

    x =\frac{5}{2}
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  3. #3
    Member Glaysher's Avatar
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    Quote Originally Posted by 1+1bob View Post
    just a quick question, what am I doing wrong here? x = 5/2


    4^(-1+1-x) = 2^3
    Here
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  4. #4
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by 1+1bob View Post
    just a quick question, what am I doing wrong here? x = 5/2

    (1/4)^(1-x) = 8


    4^(-1+1-x) = 2^3

    4^(-x) = 2^3

    2^2(-x) = 2^3

    2(-x) = 3

    -x = 3/2

    x = -3/2 ?
    the line highlighted red is where you made the mistake. you should not have added the powers, you should have multiplied them. we add powers when we multiply two numbers having the same base. here we were raising a number to a power. we multiply the powers in this case

    EDIT: Ok, Glaysher already answered your question. My apologies for butting in Glaysher
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  5. #5
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    oh ok, thanks, everything got a lot clearer now.
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