Algebra II : Understanding Logarithms

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #19 : Log Base 10

Simplify:   

Possible Answers:

Correct answer:

Explanation:

The log is in default base 10.  To simplify this log, we will need to change the base of 100 to base 10.

Rewrite the inner quantity.

We can use the additive rule of exponents since both bases are the same.

According to the rule of logs, a log of a base with similar bases will cancel, and will leave only the power.

The answer is:  

Example Question #20 : Log Base 10

Evaluate:  

Possible Answers:

Correct answer:

Explanation:

In order to eliminate the log, which has a default base of 10, we will need to raise both sides of the equation as powers using the value of 10.

The equation becomes:

Divide by three on both sides.

The answer is:  

Example Question #21 : Log Base 10

Solve:  

Possible Answers:

Correct answer:

Explanation:

Break up  using log rules.  The log has a default base of ten.

The exponent can be brought down as the coefficient since the bases of the second term are common.

This means that:  

The answer is:  

Example Question #22 : Log Base 10

Evaluate:  

Possible Answers:

Correct answer:

Explanation:

We will need to write fraction in terms of the given base of log, which is ten.

According to the log rules:

This means that the expression of log based 10 and the power can be simplified.

The answer is:  

Example Question #21 : Log Base 10

Evaluate  to the nearest tenth.

Possible Answers:

Correct answer:

Explanation:

Since most calculators only have common and natural logarithm keys, this can best be solved as follows:

By the Change of Base Property of Logarithms, if  and 

Setting , we can restate this logarithm as the quotient of two common logarithms, and calculate accordingly:

or, when rounded, 2.5. 

This can also be done with natural logarithms, yielding the same result.

Rond to one decimal place.

Example Question #24 : Log Base 10

Solve for  in the equation:

Possible Answers:

Correct answer:

Explanation:

This question tests your understanding of log functions.

 can be converted to the form .

In this problem, make sure to divide both sides by  in order to put it in the above form, where . Remember .

Therefore,

Example Question #25 : 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 : Logarithms And Exponents

Which equation is equivalent to:

Possible Answers:

Correct answer:

Explanation:

 

So, 

Example Question #2 : Logarithms And Exponents

What is the inverse of the log function?

Possible Answers:

Correct answer:

Explanation:

This is a general formula that you should memorize. The inverse of  is . You can use this formula to change an equation from a log function to an exponential function.

Example Question #3 : Logarithms And Exponents

Solve for :

Round to the nearest hundredth.

Possible Answers:

Cannot be computed

Correct answer:

Explanation:

To solve this, you need to set up a logarithm.  Our exponent is .  The logarithm's base is .  The value  is the operand of the logarithm. Therefore, we can write an equation:

Now, you cannot do this on your calculator.  Therefore, using the rule for converting logarithms, you need to change:

to...

You can put this into your calculator and get:

, or rounded, 

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