Chapter 4: Problem 19
Sketch the graph of each function. $$g(x)=\left(\frac{1}{4}\right)^{x}$$
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Chapter 4: Problem 19
Sketch the graph of each function. $$g(x)=\left(\frac{1}{4}\right)^{x}$$
These are the key concepts you need to understand to accurately answer the question.
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The graph of the function \(f(x)=C a^{x}\) passes through the points (0,12) and (2,3). (a) Use \(f(0)\) to find \(C.\) (b) Is this function increasing or decreasing? Explain. (c) Now that you know \(C\), use \(f(2)\) to find \(a\). Does your value of \(a\) confirm your answer to part (b)?
A new car that costs $$\$ 25,000$$ depreciates to $$80 \%$$ of its value in 3 years. (a) Assume the depreciation is linear. What is the linear function that models the value of this car \(t\) years after purchase? (b) Assume the value of the car is given by an exponential function \(y=A e^{h t},\) where \(A\) is the initial price of the car. Find the value of the constant \(k\) and the exponential function. (c) Using the linear model found in part (a), find the value of the car 5 years after purchase. Do the same using the exponential model found in part (b). (d) Graph both models using a graphing utility. Which model do you think is more realistic, and why?
The cost of removing chemicals from drinking water depends on how much of the chemical can safcly be left behind in the water. The following table lists the annual removal costs for arsenic in terms of the concentration of arsenic in the drinking water. (Source: Environmental Protection Agency) $$\begin{array}{|c|c|}\hline\text { Arsenic Concentration } & \text { Annual Cost } \\\\\text { (micrograms per liter) } & \text { (millions of dollars) } \\\\\hline 3 & 645 \\\5 & 379 \\\10 & 166 \\\20 & 65\\\ \hline\end{array}$$ (a) Interpret the data in the table. What is the relation between the amount of arsenic left behind in the removal process and the annual cost? (One microgram is equal to \(10^{-6}\) gram.) (b) Make a scatter plot of the data and find the exponential function of the form \(C(x)=C a^{*}\) that best fits the data. Here, \(x\) is the arscnic concentration. (c) Why must \(a\) be less than 1 in your model? (d) Using your model, what is the annual cost to obtain an arsenic concentration of 12 micrograms per liter? (e) It would be best to have the smallest possible amount of arsenic in the drinking water, but the cost may be prohibitive. Use your model to calculate the annual cost of processing such that the concentration of arsenic is only 2 micrograms per liter of water. Interpret your result.
This set of exercises will draw on the ideas presented in this section and your general math background. Do the equations \(\ln x^{2}=1\) and \(2 \ln x=1\) have the same solutions? Explain.
The decibel (dB) is a unit that is used to express the relative loudness of two sounds. One application of decibels is the relative value of the output power of an amplifier with respect to the input power. since power levels can vary greatly in magnitude, the relative value \(D\) of power level \(P_{1}\) with respect to power level \(P_{2}\) is given (in units of \(\mathrm{dB}\) ) in terms of the logarithm of their ratio as follows: $$D=10 \log \frac{P_{1}}{P_{2}}$$ where the values of \(P_{1}\) and \(P_{2}\) are expressed in the same units, such as watts \((\mathrm{W}) .\) If \(P_{2}=75 \mathrm{W},\) find the value of \(P_{1}\) at which \(D=0.7\)
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