College Algebra : Logarithmic Functions

Study concepts, example questions & explanations for College Algebra

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Example Questions

Example Question #11 : Logarithmic Functions

Expand this logarithm: \(\displaystyle \ln \frac{x^4\sqrt{y}}{z^6}\)

Possible Answers:

\(\displaystyle 4\ln x+2\ln y+6\ln z\)

\(\displaystyle 4\ln x+\frac{1}{2}\ln y-6\ln z\)

\(\displaystyle 4\ln x+\frac{1}{2}\ln y+6\ln z\)

\(\displaystyle 4\ln x+2\ln y-6\ln z\)

\(\displaystyle 4\ln x-\frac{1}{2}\ln y-6\ln z\)

Correct answer:

\(\displaystyle 4\ln x+\frac{1}{2}\ln y-6\ln z\)

Explanation:

We expand this logarithm based on the following properties:

\(\displaystyle \ln \frac{u}{v}= \ln u-\ln v\) 

 \(\displaystyle \ln u^{n}= n \ln u\)

\(\displaystyle \ln uv=\ln u+\ln v\)

 

\(\displaystyle \ln \frac{x^4\sqrt{y}}{z^6}\rightarrow \ln x^4\ln\sqrt{y}-\ln z^6\rightarrow \boldsymbol{4\ln x+\frac{1}{2}\ln y-6\ln z}\)

Example Question #21 : College Algebra

Condense this logarithm: \(\displaystyle \frac{1}{3}[2\ln (x+3)+\ln x-\ln(x^2-1)]\)

Possible Answers:

\(\displaystyle \ln\sqrt[3]{\frac{(x+3)^2}{x^2-1}}\)

\(\displaystyle \ln\sqrt[3]{\frac{x(x-3)^2}{x^2+1}}\)

None of these

\(\displaystyle \ln\sqrt[3]{\frac{x(x-3)^2}{x^2-1}}\)

\(\displaystyle \ln\sqrt[3]{\frac{x(x+3)^2}{x^2-1}}\)

Correct answer:

\(\displaystyle \ln\sqrt[3]{\frac{x(x+3)^2}{x^2-1}}\)

Explanation:

We condense this logarithm based on the following properties:

\(\displaystyle \ln \frac{u}{v}= \ln u-\ln v\) 

 \(\displaystyle \ln u^{n}= n \ln u\)

\(\displaystyle \ln uv=\ln u+\ln v\)

 

\(\displaystyle \frac{1}{3}[2\ln (x+3)+\ln x-\ln(x^2-1)]\rightarrow \frac{1}{3}[\ln(x+3)^2+\ln x-\ln(x^2-1)]\rightarrow \frac{1}{3}[ \ln x(x+3)^2-\ln (x^2-1)]\rightarrow\)

 

\(\displaystyle \frac{1}{3}[\ln\frac{x(x+3)^2}{x^2-1}]\rightarrow\boldsymbol{ \ln \sqrt[3]{\frac{x(x+3)^2}{x^2-1}}}\)

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