SOLUTION: Express as a single log 7^log base 7 45 + log base 6 3600

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Question 425890: Express as a single log
7^log base 7 45 + log base 6 3600

Answer by jsmallt9(3758) About Me  (Show Source):
You can put this solution on YOUR website!
7%5Elog%287%2C+%2845%29%29+%2B+log%286%2C+%283600%29%29
Once you understand logarithms you will find the first term ridiculously easy to simplify.

Generally logarithms are exponents. log%28a%2C+%28b%29%29 represents the exponent for "a" that results in "b". In other "words", a%5Elog%28a%2C+%28b%29%29+=+b by definition of what a logarithm is!.

So 7%5Elog%287%2C+%2845%29%29+=+45 by definition. Now your expression is:
45+%2B+log%286%2C+%283600%29%29
This is a single logarithm expression so it may be an acceptable answer. But the second logarithm can be simplified, too, because its argument, 3600, has a power of 6 factor:
45+%2B+log%286%2C+%2836%2A100%29%29
45+%2B+log%286%2C+%2836%29%29+%2Blog%286%2C+%28100%29%29
45+%2B+log%286%2C+%286%5E2%29%29+%2Blog%286%2C+%28100%29%29
45+%2B+2+%2Blog%286%2C+%28100%29%29
47+%2Blog%286%2C+%28100%29%29
This is a simplified, single logarithm expression.

If the problem is literally to write the expression as just a single logarithm, then we need both terms to be in terms of base 6 logarithms. Since log%286%2C+%286%29%29+=+1 and since multiplying by a 1 (no matter what form it is in) does not change a number we can rewrite the expression as:
47%2Alog%286%2C+%286%29%29+%2Blog%286%2C+%28100%29%29
Now we can use a property of logarithms, q%2Alog%28a%2C+%28p%29%29+=+log%28a%2C+%28p%5Eq%29%29 to move the coefficient of the first logarithm in the argumetn as its exponent:
log%286%2C+%286%5E47%29%29+%2Blog%286%2C+%28100%29%29
Now we can use another property of logarithms, log%28a%2C+%28p%29%29+%2B+log%28a%2C+%28q%29%29, to combine the two logarithms into one. (This property requires that the two logarithms have the same base (which is why we introduced the base 6 log to the first term) and coefficients of 1 (which is why we used the other property to move the 47 into the argument)) Using this property to combine the two logarithms we get:
log%286%2C+%286%5E47%2A100%29%29
or
log%286%2C+%28100%2A6%5E47%29%29