logarithm equation help.

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February 10th 2013, 04:59 AM
agehayoshina

logarithm equation help.

the equations in question are log₄(x+1)-log₄3=1 and 4(7^x)-7^2x=3

not sure what method to use to approach these.

thanks

age
February 10th 2013, 05:21 AM
Plato

Re: logarithm equation help.

Quote:

Originally Posted by agehayoshina

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

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

The second is equivalent to $u^2-4u+3=0$ where $u=7^x$ .
February 10th 2013, 05:37 AM
agehayoshina

Re: logarithm equation help.

Could you please explain how you got to those answers?
February 10th 2013, 05:49 AM
HallsofIvy

Re: logarithm equation help.

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

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

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