Algebra II : Mathematical Relationships and Basic Graphs

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #12 : Logarithms And Exponents

Simplify:  \displaystyle 2ln(e^3)

Possible Answers:

\displaystyle 2e^6

\displaystyle 5

\displaystyle 6

\displaystyle e^6

\displaystyle e^5

Correct answer:

\displaystyle 6

Explanation:

When the base \displaystyle e is raised to a certain power, taking the natural log of this whole term will eliminate the exponential and the power can be pulled out as the coefficient.

\displaystyle 2ln(e^3) = 2(3) ln(e^1) = 2(3)= 6

The answer is:  \displaystyle 6

Example Question #59 : Understanding Logarithms

Solve:  \displaystyle log_{\frac{1}{5}} 125

Possible Answers:

\displaystyle -3

\displaystyle -\frac{3}{5}

\displaystyle -\frac{3}{125}

\displaystyle -\frac{5}{3}

\displaystyle -\frac{1}{3}

Correct answer:

\displaystyle -3

Explanation:

In order to solve this log, we will need to write 125 in terms of one fifth to a certain power.

Rewrite 125 as an exponent of one-fifth.

\displaystyle 125 = (\frac{1}{5})^{-3}

\displaystyle log_{\frac{1}{5}} 125=log_{\frac{1}{5}}(\frac{1}{5})^{-3}

According to the log rule,  \displaystyle log_{x}x^y=y, the bases will cancel, leaving just the exponent.

The answer is:  \displaystyle -3

Example Question #61 : Understanding Logarithms

Simplify, if possible:  \displaystyle 2log(125)

Possible Answers:

\displaystyle 5log(5)

\displaystyle 10log(3)

\displaystyle 6log(3)

\displaystyle 6log(5)

Correct answer:

\displaystyle 6log(5)

Explanation:

Notice that the term in the log can be rewritten as a base raised to a certain power.

Rewrite the number in terms of base five.

\displaystyle 2log(125)=2log(5^3)

According to log rules, the exponent can be dropped as a coefficient in front of the log.

\displaystyle 2\cdot 3log(5) = 6log(5)

The answer is:  \displaystyle 6log(5)

Example Question #62 : Understanding Logarithms

Solve:  \displaystyle 3log_{5}(5^{10})

Possible Answers:

\displaystyle 30

\displaystyle 18

\displaystyle 13

\displaystyle 1000

\displaystyle 300

Correct answer:

\displaystyle 30

Explanation:

Evaluate the log using the following property:

\displaystyle log_xx^y = y

The log based and the base of the term will simplify.

The expression becomes: 

\displaystyle 3log_{5}(5^{10}) = 3(10) = 30

The answer is:  \displaystyle 30

Example Question #61 : Understanding Logarithms

Try to answer without a calculator.

True or false:

\displaystyle \log_{7} 700 = 2

Possible Answers:

True

False

Correct answer:

False

Explanation:

By definition, \displaystyle \log_{7} 700 = 2 if and only if \displaystyle 7^{2} = 700. However, 

\displaystyle 7^{2} = 7 \times 7 = 49 \ne 700,

making this false.

Example Question #62 : Logarithms

Try without a calculator:

Evaluate \displaystyle \log_{16} 8

Possible Answers:

\displaystyle -\frac{4}{3}

\displaystyle -\frac{3}{4}

\displaystyle \frac{4}{3}

None of the other choices gives the correct response.

\displaystyle \frac{3}{4}

Correct answer:

\displaystyle \frac{3}{4}

Explanation:

By definition, \displaystyle \log_{16} 8 = N if and only if \displaystyle 16^{N} = 8.

8 and 16 are both powers of 2; specifically, \displaystyle 8= 2^{3} , 16 = 2^{4}. The latter equation can be rewritten as

\displaystyle \left (2 ^{4} \right ) ^{N} = 2^{3}

By the Power of a Power Property, the equation becomes

\displaystyle 2 ^{4\cdot N} = 2^{3}

or

\displaystyle 2 ^{4N} = 2^{3}

It follows that

\displaystyle 4N = 3,

and

\displaystyle N = \frac{3}{4},

the correct response.

Example Question #65 : Understanding Logarithms

Solve for \displaystyle N (nearest tenth):

\displaystyle \log_{7} N = 1.8.

Possible Answers:

\displaystyle 2.9

\displaystyle 61.2

\displaystyle 33.2

\displaystyle 12.6

Correct answer:

\displaystyle 33.2

Explanation:

By definition, \displaystyle \log_{a}N = M if and only if \displaystyle a^{M}= N. Set \displaystyle a= 7, M = 1.8, and

\displaystyle \log_{7} N = 1.8

if and only if

\displaystyle N= 7^{1.8}

Through calculation, we see that

\displaystyle N \approx 33.2.

Example Question #61 : Logarithms

Try to answer without a calculator:

Which is true about \displaystyle \log_{0}1?

Possible Answers:

\displaystyle \log_{0}1 = 0

\displaystyle \log_{0}1 is an undefined quantity

\displaystyle \log_{0}1 = 1

Cannot be determined

Correct answer:

\displaystyle \log_{0}1 is an undefined quantity

Explanation:

The question asks for the value of the "base 0 logarithm" of 0. However, this is not defined, as a logarithm can only have as its base a positive number not equal to 1. 

Example Question #67 : Understanding Logarithms

Given the following:

\displaystyle \log_{8} M = N

Decide if the following expression is true or false:

\displaystyle \log_{M} 8 = \frac{1}{N} for all positive \displaystyle M.

Possible Answers:

True

False

Correct answer:

True

Explanation:

By definition of a logarithm,

\displaystyle \log_{8} M = N 

if and only if 

\displaystyle 8^{N } = M

Take the \displaystyle Nth root of both sides, or, equivalently, raise both sides to the power of \displaystyle \frac{1}{N}, and apply the Power of a Power Property:

\displaystyle \left (8^{N } \right ) ^{\frac{1}{N}} = M ^{\frac{1}{N}}

\displaystyle 8^{N \cdot \frac{1}{N} } = M ^{\frac{1}{N}}

\displaystyle 8^{1 } = M ^{\frac{1}{N}}

or

\displaystyle M ^{\frac{1}{N}} = 8

By definition, it follows that \displaystyle \log_{M} 8 = \frac{1}{N}, so the statement is true.

 

Example Question #68 : Understanding Logarithms

\displaystyle \log_{N }10 = M, with \displaystyle N positive and not equal to 1.

Which of the following is true of \displaystyle \log_{N }100 for all such \displaystyle N ?

Possible Answers:

\displaystyle \log_{N }100 = \frac{M}{2}

\displaystyle \log_{N }100 = 2M

\displaystyle \log_{N }100 = M^{2}

\displaystyle \log_{N }100 = M + 2

\displaystyle \log_{N }100 = M + 1

Correct answer:

\displaystyle \log_{N }100 = 2M

Explanation:

By definition,

\displaystyle \log_{N }10 = M

If and only if

\displaystyle N^{M}= 10

Square both sides, and apply the Power of a Power Property to the left expression:

\displaystyle (N^{M})^{2}= 10^{2}

\displaystyle N^{M\cdot 2}= 100

\displaystyle N^{2M}= 100

It follows that for all positive \displaystyle N not equal to 1,

\displaystyle \log_{N }100 = 2M 

for all \displaystyle N.

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