Chapter 4: Problem 4
Write \(\ln (x+4)=6\) in exponential form.
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Chapter 4: Problem 4
Write \(\ln (x+4)=6\) in exponential form.
These are the key concepts you need to understand to accurately answer the question.
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Sounds are produced when vibrating objects create pressure waves in some medium such as air. When these variations in pressure reach the human eardrum, it causes the eardrum to vibrate in a similar manner and the ear detects sound. The intensity of sound is measured as power per unit area. The threshold for hearing (minimum sound detectable by a young, healthy ear) is defined to be \(I_{0}=10^{-12} \mathrm{~W} / \mathrm{m}^{2}\) (watts per square meter). The sound level \(L,\) or "loudness" of sound, is measured in decibels \((\mathrm{dB})\) as \(L=10 \log \left(\frac{I}{I_{0}}\right),\) where \(I\) is the intensity of the given sound. Use this formula for exercises. a. Find the sound level of a jet plane taking off if its intensity is \(10^{15}\) times the intensity of \(I_{0}\). b. Find the sound level of the noise from city traffic if its intensity is \(10^{9}\) times \(I_{0}\). c. How many times more intense is the sound of a jet plane taking off than noise from city traffic?
Explain why the domain of \(f(x)=x^{2}+k\) must be restricted to find an inverse function.
Determine if the statement is true or false. For each false statement, provide a counterexample. For example, \(\log (x+y) \neq \log x+\log y\) because \(\log (2+8) \neq \log 2+\log 8\) (the left side is 1 and the right side is approximately 1.204 ). $$ \log _{5}\left(\frac{1}{x}\right)=\frac{1}{\log _{5} x} $$
Fluorodeoxyglucose is a derivative of glucose that contains the radionuclide fluorine- \(18\left({ }^{18} \mathrm{~F}\right) .\) A patient is given a sample of this material containing \(300 \mathrm{MBq}\) of \({ }^{18} \mathrm{~F}\) (a megabecquerel is a unit of radioactivity). The patient then undergoes a PET scan (positron emission tomography) to detect areas of metabolic activity indicative of cancer. After \(174 \mathrm{~min}\), one-third of the original dose remains in the body. a. Write a function of the form \(Q(t)=Q_{0} e^{-k t}\) to model the radioactivity level \(Q(t)\) of fluorine- 18 at a time \(t\) minutes after the initial dose. b. What is the half-life of \({ }^{18} \mathrm{~F}\) ?
\(F(C)=\frac{9}{5} C+32\) gives the temperature in degrees Fahrenheit as a function of the temperature \(C\) in degrees Celsius. Find an equation for \(C(F)\) and interpret its meaning in the context of this problem.
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