Algebra II : Natural Log

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #21 : Natural Log

Solve:  \displaystyle ln(2x-e) = 3

Possible Answers:

\displaystyle \frac{e^3+e}{2}

\displaystyle \frac{(e+1)^3}{2}

\displaystyle \frac{e^3-e}{2}

\displaystyle \frac{3}{2}e

\displaystyle \frac{9-e}{3}

Correct answer:

\displaystyle \frac{e^3+e}{2}

Explanation:

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

\displaystyle e^{ln(2x-e)} = e^3

The equation can be simplified to:

\displaystyle 2x-e = e^3

Add \displaystyle e on both sides.

\displaystyle 2x-e +e= e^3+e

\displaystyle 2x= e^3+e

Divide by two on both sides.

\displaystyle \frac{2x}{2}= \frac{e^3+e}{2}

The answer is:  \displaystyle \frac{e^3+e}{2}

Example Question #261 : Mathematical Relationships And Basic Graphs

Try without a calculator:

Which expression is not equivalent to 1?

Possible Answers:

\displaystyle 1,000,000^{0}

\displaystyle \log 10

\displaystyle i^{4}

\displaystyle 1,000^{\frac{1}{1,000}}

\displaystyle \ln e

Correct answer:

\displaystyle 1,000^{\frac{1}{1,000}}

Explanation:

\displaystyle 1,000^{\frac{1}{1,000}} is the correct choice.

For all \displaystyle a,N for which the expressions are defined, 

\displaystyle a ^{\frac{1}{N}} = \sqrt[N]{a}.

Setting \displaystyle a=1,000, N = 1,000, this equation becomes

\displaystyle 1,000 ^{\frac{1}{1,000}} = \sqrt[1,000]{1,000} - that is, the one thousandth root of 1,000. This is not equal to 1, since if it were, it would hold that \displaystyle 1^{1,000} = 1,000 - which is not true. 

 

Of the other four expressions:

\displaystyle \log 10, the common, or base ten, logarithm of 10, can be rewritten as \displaystyle \log_{10}10, and \displaystyle \ln e, the natural, or base \displaystyle e, logarithm of \displaystyle e, can be rewritten as \displaystyle \log_{e}e. A property of logarithms states that for all \displaystyle N > 0, N \ne 1\displaystyle \log_{N}N = 1. Therefore, \displaystyle \log 10 = \log_{10}10 = 1 and  \displaystyle \ln e = \log_{e}e = 1.

 

\displaystyle 1,000,000^{0} = 1, since any nonzero number raised to the power of 0 is equal to 1.

 

By the Power of a Power Property, 

\displaystyle i^{4} = i ^{2 \cdot 2} =( i^{2} )^{2}

\displaystyle i^{2} = -1, so

\displaystyle i^{4} = ( -1)^{2}= 1

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