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Example Questions
Example Question #161 : Logarithms
If and , what is ?
First, we know from logarithmic properties that:
So if we can find a combination of our knowns that equal , we should be able to figure out . It may take some guess and check, but:
That would equate to:
Using our log properties, we can simplify into:
That means that:
Example Question #27 : Solving Logarithms
Evaluate .
There are a few ways to go about this, but let's use a change of base to make the problem easier to work without using a calculator. First, we know that:
We can choose any value for that we would like here, so to make things simple, let's put this problem in base :
Example Question #28 : Solving Logarithms
Evaluate .
We can take this problem and expand it a bit, which will make things easier in the long run. We know that:
Using one of our logarithmic properties, we can expand even further:
Another log property states that:
So:
Example Question #21 : Solving And Graphing Logarithms
Solve:
To solve for x, remember that exponents inside logarithms can be moved to the front of the logarithm:
Next, we can rewrite the logarithm as the number it equals, and solve for x:
Example Question #22 : Solving And Graphing Logarithms
Solve:
In order to solve for the x-variable, we will need to exponential function both sides of the equation in order to eliminate the natural log.
The equation becomes:
Divide by two on both sides.
The answer is:
Example Question #3071 : Algebra Ii
Expand the log:
Rewrite the logarithm using the quotient property.
Rewrite the log.
Use the power property to pull down the power.
Simplify the log terms.
The answer is:
Example Question #3072 : Algebra Ii
Solve for :
None of these
Using definition of logarithms:
Example Question #3073 : Algebra Ii
Solve for :
None of these
Using definition of logarithms
Example Question #31 : Solving And Graphing Logarithms
Solve the following equation:
Recall the definition of a logarithm. For a logarithm in any base ,
denotes
.
In other words, the value of a logarithm is simply an exponent, and it is defined at whenever the base can be raised to a sufficient power to yield . Hence, the equation
may be rewritten as
.
Raising to the th power yields , and so
.
Example Question #32 : Solving Logarithms
Solve the following equation:
According to the rule for multiplying logarithms, for any constant value . In other words, an exponent on the quantity inside a logarithm can be moved outside the logarithm as a multiplier, and vice versa. Hence,
.
Since the natural logarithm has as its base, the definition of logarithms applies in this case: whenever the base of is equal to .
.
This implies that and . However, substituting the solution into the original equation yields the following expression:
which is not defined, since logarithms are undefined for any value of .
Hence, we eliminate the extraneous solution and submit that the correct solution to this equation is .
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