Algebra II : Understanding Logarithms

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #21 : Natural Log

Solve:  

Possible Answers:

Correct answer:

Explanation:

In order to eliminate the natural log, which has a base of , we will need to raise both side as powers of .

The equation can be simplified to:

Add  on both sides.

Divide by two on both sides.

The answer is:  

Example Question #22 : Natural Log

Try without a calculator:

Which expression is not equivalent to 1?

Possible Answers:

Correct answer:

Explanation:

 is the correct choice.

For all  for which the expressions are defined, 

.

Setting , this equation becomes

 - that is, the one thousandth root of 1,000. This is not equal to 1, since if it were, it would hold that  - which is not true. 

 

Of the other four expressions:

, the common, or base ten, logarithm of 10, can be rewritten as , and , the natural, or base , logarithm of , can be rewritten as . A property of logarithms states that for all . Therefore,  and  .

 

, since any nonzero number raised to the power of 0 is equal to 1.

 

By the Power of a Power Property, 

, so

Example Question #1 : Logarithms

Based on the definition of logarithms, what is  ? 

Possible Answers:

10

2

4

100

3

Correct answer:

3

Explanation:

For any equation , . Thus, we are trying to determine what power of 10 is 1000. , so our answer is 3. 

Example Question #1 : Log Base 10

Evaluate .

Possible Answers:

Correct answer:

Explanation:

Take the common logarithm of both sides, and take advantage of the property of the logarithm of a power:

Example Question #1 : Log Base 10

What is the value of ?

Possible Answers:

Correct answer:

Explanation:

Base-10 logarithms are very easy if the operands are a power of .  Begin by rewriting the question:

Becomes...

because 

Applying logarithm rules, you can factor out the :

Now,  is .

Therefore, your answer is .

Example Question #1 : Log Base 10

What is the value of ?

Round to the nearest hundreth.

Possible Answers:

Correct answer:

Explanation:

Base-10 logarithms are very easy if the operands are a power of .  Begin by rewriting the question:

Becomes...

because 

Applying logarithm rules, you can factor out the :

Now,  is .

Therefore, your answer is .

Example Question #1 : Log Base 10

Many textbooks use the following convention for logarithms: 

What is the value of ?

Possible Answers:

Correct answer:

Explanation:

Remember:

 is the same as saying .

So when we ask "What is the value of ?", all we're asking is "10 raised to which power equals 1,000?" Or, in an expression: 

.

From this, it should be easy to see that .

Example Question #1 : Log Base 10

Evaluate the following expression:

 

Possible Answers:

Correct answer:

Explanation:

Without a subscript a logarithmic expression is base 10.

The expression  

The logarithmic expression is asking 10 raised to what power equals 1000 or what is x when

We know that

so 

Example Question #7 : Log Base 10

Assuming the value of  is positive, simplify:  

Possible Answers:

Correct answer:

Explanation:

Rewrite the logarithm in division.

As a log property, we can pull down the exponent of the power in front as the coefficient.

Cancel out the .

The answer is:  

Example Question #8 : Log Base 10

Solve the following:

Possible Answers:

Correct answer:

Explanation:

When the base isn't explicitly defined, the log is base 10. For our problem, the first term

is asking:

For the second term,

is asking:

So, our final answer is

 

 

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