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Thread: logarithm equation help.

  1. #1
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    Question logarithm equation help.

    the equations in question are log4(x+1)-log43=1 and 4(7x)-72x=3



    not sure what method to use to approach these.

    thanks

    age
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  2. #2
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    Re: logarithm equation help.

    Quote Originally Posted by agehayoshina View Post
    the equations in question are $\displaystyle \log_4(x+1)-\log_4(3)=1$ and $\displaystyle 4(7^x)-7^{2x}=3$
    not sure what method to use to approach these.

    The first one is $\displaystyle \frac{x+1}{3}=4$.

    The second is equivalent to $\displaystyle u^2-4u+3=0$ where $\displaystyle u=7^x$.
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  3. #3
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    Re: logarithm equation help.

    Could you please explain how you got to those answers?
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  4. #4
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    Re: logarithm equation help.

    In the first problem Plato used the fact that $\displaystyle log a- log b= log(a/b)$ and that $\displaystyle log_b(b)= 1$.

    For the second, he substituted y for $\displaystyle 7^x$, as he said, and used the fact that $\displaystyle 7^{2x}= (7^x)^2= y^2$.
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