SOLUTION: (log4(log4^x))=-4

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Question 238662: (log4(log4^x))=-4
Answer by jsmallt9(3758) About Me  (Show Source):
You can put this solution on YOUR website!
log%284%2C+%28log%284%2C+%28x%29%29%29%29+=+-+4
Solving equations of the form
log(some-expression-with-a-variable) = another-expression
is usually done by rewriting the equaiton in exponential form. To rewrite logarithmic equations in logarithmic form we need to remember that log%28a%2C+%28p%29%29+=+q is equivalent to p+=+a%5Eq

Since your equation has a logarithm within a logarithm, we will have to do this twice. Rewriting the outer logarithm in exponential form we get:
log%284%2C+%28x%29%29+=+4%5E%28-4%29
Since 4%5E%28-4%29+=+1%2F%284%5E4%29 and 4%5E4+=+4%2A4%2A4%2A4+=+256, the right side simplifies to:
log%284%2C+%28x%29%29+=+1%2F256
Now we will rewrite the remaining logarithm in exponential form:
x+=+4%5E%281%2F256%29
This may be an acceptable form for the answer. But it can be simplified a little. First we can "reduce" the exponent using a bit of cleverness and a good understanding of fractional exponents:
Factor the exponent:
x+=+4%5E%28%281%2F2%29%281%2F128%29%29
Use the property a%5E%28p%2Aq%29+=+%28a%5Ep%29%5Eq to rewrite the abvoe as a power of a power:
x+=+%284%5E%281%2F2%29%29%5E%281%2F128%29
Since 4%5E%281%2F2%29+=+sqrt%284%29 and sqrt%284%29+=+2, we can replace 4%5E%281%2F2%29 with 2. (This is why we factored 1/2 out of the exponent.)
x+=+2%5E%281%2F128%29
This is a simplified form of the answer. With a fractional exponent, we could write this in radical form:
x+=+root%28128%2C+2%29