SOLUTION: Solve for x in (125)^x=625 I'm completely lost on this

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Question 86947: Solve for x in (125)^x=625
I'm completely lost on this

Answer by bucky(2189) About Me  (Show Source):
You can put this solution on YOUR website!
Anytime you see an equation that has a variable in the exponent, one of the first things
you should think of is "logarithms"
.
You are given:
.
%28125%29%5Ex=625
.
Take the logarithm of both sides of this equation. You can use base 10 or base e, which is
"ln" or natural logarithms. These can be worked on a normal scientific calculator so either
is a good choice. Let's choose base 10. Taking the Log base 10 of both sides of the equation
results in:
.
Log%5B10%5D125%5Ex+=+Log%5B10%5D625
.
To simplify things a little, let's use a calculator to find Log%5B10%5D625. Enter 625
on the calculator and press the "log" key. You should get 2.795880017. Substituting
this value results in the equation becoming:
.
Log%5B10%5D125%5Ex+=+2.795880017
.
Next we'll use another property of logarithms. If you are finding the logarithm of a quantity
that has an exponent, an equivalent form is to multiply the logarithm by the exponent.
In other words, Log%5B10%5D125%5Ex is equivalent to x%2ALog%5B10%5D125 so let's substitute
that into our equation to get:
.
x%2ALog%5B10%5D125+=+2.795880017
.
Now use a calculator to find Log%5B10%5D125. Enter 125 and press the "log" key to get
Log%5B10%5D125+=+2.096910013. Substitute this into the equation and you now have:
.
x%2A2.096910013+=+2.795880017
.
Finally divide both sides by 2.096910013 and the answer becomes:
.
x+=+2.795880017%2F2.096910013+=+1.333333333 and this is 4%2F3
.
Hope this helps you with your understanding of logarithms.