Chapter 9: Problem 106
Solve \(\log _{8}(2 x+1)=-1\)
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Chapter 9: Problem 106
Solve \(\log _{8}(2 x+1)=-1\)
These are the key concepts you need to understand to accurately answer the question.
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The decay rate of krypton- 85 is \(6.3 \%\) per year. What is its half-life?
The number of computers infected by a virus \(t\) days after it first appears usually increases exponentially. In 2009 the "Conflicker" worm spread from about 2.4 million computers on January 12 to about 3.2 million computers on January \(13 .\) Data: PC World a) Find the exponential growth rate \(k\) and write an equation for an exponential function that can be used to predict the number of computers infected \(t\) days after January \(12,2009\) b) Assuming exponential growth, estimate how long it took the Conflicker worm to infect 10 million computers.
The atmospheric pressure in the lower stratosphere decreases exponentially from 473 lb \(/ \mathrm{ft}^{2}\) at \(36,152 \mathrm{ft}\) to \(51 \mathrm{lb} / \mathrm{ft}^{2}\) at \(82,345 \mathrm{ft}\) Data: grc.nasa.gov a) Find the exponential decay rate \(k,\) and write an equation for an exponential function that can be used to estimate the atmospheric pressure in the stratosphere \(h\) feet above \(36,152\) ft. b) Estimate the atmospheric pressure at \(50,000 \mathrm{ft}\) \((h=50,000-36,152)\) c) At what height is the atmospheric pressure \(100 \mathrm{lb} / \mathrm{ft}^{2} ?\) d) What change in altitude will result in atmospheric pressure being halved?
Atmospheric pressure \(P\) at an elevation \(a\) feet above sea level can be estimated by $$ P=P_{0} e^{-0.00004 a} $$ where \(P_{0}\) is the pressure at sea level, which is approximately 29.9 in. of mercury (Hg). Explain how a barometer, or some other device for measuring atmospheric pressure, can be used to find the height of a skyscraper.
The concentration of acetaminophen in the body decreases exponentially after a dosage is given. In one clinical study, adult subjects averaged 11 micrograms \(/\) milliliter \((\mathrm{mcg} / \mathrm{mL})\) of the drug in their blood plasma 1 hr after a 1000 -mg dosage and 2 micrograms / milliliter 6 hr after dosage. Data: tylenolprofessional.com; Mark Knopp, M.D. a) Find the value \(k,\) and write an equation for an exponential function that can be used to predict the concentration of acetaminophen, in micrograms / milliliter, t hours after a 1000 -mg dosage. b) Estimate the concentration of acetaminophen 3 hr after a 1000 -mg dosage. c) To relieve a fever, the concentration of acetaminophen should go no lower than \(4 \mathrm{mcg} / \mathrm{mL}\). After how many hours will a 1000 -mg dosage drop to that level? d) Find the half-life of acetaminophen.
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