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Math Help - explanation of algebra question

  1. #1
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    explanation of algebra question

    hi there, trying to understand this expression.

    5^{4-x}

    is the same as:
     <br /> <br />
= (\frac{1}{5})^{x-4}<br />

    im not really understanding what it does to get that. any1 ? thank u
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  2. #2
    A riddle wrapped in an enigma
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    Quote Originally Posted by jvignacio View Post
    hi there, trying to understand this expression.

    5^{4-x}

    is the same as:
     <br /> <br />
= (\frac{1}{5})^{x-4}<br />

    im not really understanding what it does to get that. any1 ? thank u

    One of the laws of exponents says:

    a^{m}=\left(\frac{1}{a}\right)^{-m} \ \ or \ \ \left(\frac{a}{b}\right)^{-m}=\left(\frac{b}{a}\right)^m

    5^{4-x}=\left(\frac{1}{5}\right)^{-(4-x)}=\left(\frac{1}{5}\right)^{(-4+x)}=\left(\frac{1}{5}\right)^{(x-4)}


    Last edited by masters; November 26th 2008 at 08:45 AM.
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  3. #3
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    Quote Originally Posted by masters View Post
    One of the laws of exponents says:

    a^{m}=\left(\frac{1}{a}\right)^{-m} \ \ or \ \ \left(\frac{a}{b}\right)^{-m}=\left(\frac{b}{a}\right)^m

    5^{4-x}=\left(\frac{1}{5}\right)^{-(4-x)}=\left(\frac{1}{5}\right)^{(-4+x)}=\left(\frac{1}{5}\right)^{(x+4)}

    oh mate just wat i needed. cheers.
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  4. #4
    A riddle wrapped in an enigma
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    Quote Originally Posted by jvignacio View Post
    oh mate just wat i needed. cheers.
    I changed a sign in my original answer in the last step. Exponent should be x-4, not x+4. Sorry. Typing too fast. My original post is correct now.
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