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Thread: logarithm

  1. #1
    Newbie Zharif93's Avatar
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    logarithm

    5^(2x) + 5^(3x-1) = 150
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  2. #2
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    Are you sure this isn't supposed to be

    $\displaystyle 5^{2x} \cdot 5^{3x-1} = 150$?
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  3. #3
    Newbie Zharif93's Avatar
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    im not sure , my friend ask me this question
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  4. #4
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    $\displaystyle 5^{2z}= (5^x)^2$ and $\displaystyle 5^{3x-1}= \frac{(5^x)^3}{5}$

    Your equation is $\displaystyle (5^x)^2+ \frac{(5^x)^3}{5}= 150$. If you let $\displaystyle y= 5^x$ you have $\displaystyle y^2+ y^3/5= 150$ or the cubic polynomial $\displaystyle y^3+ 5y^2= 750$. Any rational solution for y must be a factor of 750. I suggest you whack your friend about the ears!
    Last edited by mr fantastic; Jul 17th 2010 at 03:08 PM.
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