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:

\(\displaystyle 5log(5)\)

\(\displaystyle 10log(3)\)

\(\displaystyle \textup{The answer is already simplified.}\)

\(\displaystyle 6log(3)\)

\(\displaystyle 6log(5)\)

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:

False

True

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 #301 : Mathematical Relationships And Basic Graphs

Try to answer without a calculator:

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

Possible Answers:

\(\displaystyle \log_{0}1 = 1\)

Cannot be determined

\(\displaystyle \log_{0}1 = 0\)

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

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 \(\displaystyle N\)th 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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