/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 12 Write each equation in exponenti... [FREE SOLUTION] | 91Ó°ÊÓ

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Write each equation in exponential form. (a) \(\ln u=s\) (b) \(\log _{a} b=c\)

Short Answer

Expert verified
(a) \(u = e^s\), (b) \(b = a^c\)

Step by step solution

01

Understand Natural Logarithm

The natural logarithm of a number \(u\), denoted as \(\ln u\), is the power to which the base \(e\) (Euler's number, approximately 2.718) must be raised to equal \(u\). The equation \( \ln u = s \) implies that \( e^s = u \).
02

Convert First Equation to Exponential Form

Given \( \ln u = s \), rewrite it in exponential form by expressing \( u \) as \( u = e^s \).
03

Understand Logarithm with Arbitrary Base

For a logarithm \( \log_a b = c \), this implies that \( a \), the base, raised to the power \(c\), equals \(b\).
04

Convert Second Equation to Exponential Form

Given \( \log_a b = c \), rewrite it in exponential form by expressing \( b \) as \( b = a^c \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Natural Logarithm
The natural logarithm is a special kind of logarithm that uses a unique base, known as Euler's number, denoted by \(e\). This base is approximately equal to 2.718. The natural logarithm is represented as \(\ln(u)\). It shows how many times you need to multiply \(e\) to get the number \(u\). For example, if \(\ln(u) = s\), it means \(e\) raised to the power of \(s\) equals \(u\), or \(e^s = u\).

In simpler terms, the natural logarithm answers the question: "What power do we need to raise \(e\) to, in order to get \(u\)?" This concept is widely used in mathematics, especially in calculus and exponential growth problems.

  • The natural log function grows slowly but steadily, matching the nature of exponential growth.
  • It is very useful for simplifying complex equations involving exponential functions.
Understanding the natural logarithm is crucial because it forms the basis of many equations in natural sciences, making it an essential part of mathematical studies.
Euler's Number
Euler's number, often denoted as \(e\), is a fundamental mathematical constant. It is characterized by being the base of the natural logarithm, and it appears frequently in different branches of mathematics, especially in calculus and complex analysis.

This number is irrational, meaning it goes on forever without repeating. Approximated to 2.718, it provides a natural scaling factor for mathematical growth processes.

  • In the expression \(e^x\), \(e\) is used as the base of the exponential function, which increases rapidly for positive \(x\) values and decreases for negative ones.
  • Euler's number is central to the natural pinning of logarithmic processes because it reflects a standard growth rate.
The uniqueness of \(e\) lies in its properties, such as the rate of change at the boundary between algebra and calculus. This makes \(e\) vital for solving problems involving continuously growing or decaying quantities, such as populations or radioactive substances.
Logarithm with Arbitrary Base
Logarithms allow us to solve for the exponent needed to achieve a particular number, using any chosen base. The notation \(\log_a(b) = c\) means that \(a\), raised to the power \(c\), results in \(b\), or \(a^c = b\). This is hugely useful for making calculations easier, by transforming multiplication operations into additions.

Logarithms with arbitrary bases extend the concept beyond the natural and common logarithms. These can be any number, and understanding them helps in fields such as computer science, finance, and engineering, where different scales or systems may be used.

  • Changing the base of a logarithm can make complicated arithmetic simpler and more manageable.
  • It's crucial for understanding logarithmic scales, like pH in chemistry or the Richter scale in seismology.
Mastering arbitrary base logarithms offers a deeper insight into mathematical relationships. They stand as a bridge between real-world applications and theoretical math, providing a robust tool for analyzing growth and decay across various contexts.

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Most popular questions from this chapter

Solve the equations. \(x^{\left(x^{\prime}\right)}=\left(x^{x}\right)^{x}\) Hint: There are two solutions.

Exercises \(55-60\) introduce a model for population growth that takes into account limitations on food and the environment. This is the logistic growth model, named and studied by the nineteenth century Belgian mathematician and sociologist Pierre Verhulst. (The word "logistic" has Latin and Greek origins meaning "calculation" and "skilled in calculation," respectively. However, that is not why Verhulst named the curve as he did. See Exercise 56 for more about this.) In the logistic model that we "I study, the initial population growth resembles exponential growth. But then, at some point owing perhaps to food or space limitations, the growth slows down and eventually levels off, and the population approaches an equilibrium level. The basic equation that we'll use for logis- tic growth is where \(\mathcal{N}\) is the population at time \(t, P\) is the equilibrium population (or the upper limit for population), and a and b are positive constants. $$\mathcal{N}=\frac{P}{1+a e^{-b t}}$$ The following figure shows the graph of the logistic function \(\mathcal{N}(t)=4 /\left(1+8 e^{-t}\right) .\) Note that in this equation the equilibrium population \(P\) is 4 and that this corresponds to the asymptote \(\mathcal{N}=4\) in the graph. (a) Use the graph and your calculator to complete the following table. For the values that you read from the graph, estimate to the nearest \(0.25 .\) For the calculator values, round to three decimal places. (b) As indicated in the graph, the line \(\mathcal{N}=4\) appears to be an asymptote for the curve. Confirm this empirically by computing \(\mathcal{N}(10), \mathcal{N}(15),\) and \(\mathcal{N}(20) .\) Round each answer to eight decimal places. (c) Use the graph to estimate, to the nearest integer, the value of \(t\) for which \(\mathcal{N}(t)=3\) (d) Find the exact value of \(t\) for which \(\mathcal{N}(t)=3 .\) Evaluate the answer using a calculator, and check that it is consistent with the result in part (c). TABLE AND GRAPH CANT COPY

The Chernobyl nuclear explosion (in the former Soviet Union, on April 26,1986 ) released large amounts of radioactive substances into the atmosphere. These substances included cesium-137, iodine-131, and strontium-90. Although the radioactive material covered many countries, the actual amount and intensity of the fallout varied greatly from country to country, due to vagaries of the weather and the winds. One area that was particularly hard hit was Lapland, where heavy rainfall occurred just when the Chernobyl cloud was overhead. (a) Many of the pastures in Lapland were contaminated with cesium-137, a radioactive substance with a half- life of 33 years. If the amount of cesium- 137 was found to be ten times the normal level, how long would it take until the level returned to normal? Hint: Let \(\mathcal{N}_{0}\) be the amount that is ten times the normal level. Then you want to find the time when \(\mathcal{N}(t)=\mathcal{N}_{0} / 10\) (b) Follow part (a), but assume that the amount of cesium-137 was 100 times the normal level. Remark: Several days after the explosion, it was reported that the level of cesium- 137 in the air over Sweden was 10,000 times the normal level. Fortunately there was little or no rainfall.

(a) Use a graphing utility to estimate the root(s) of the equation to the nearest one-tenth (as in Example 6). (b) Solve the given equation algebraically by first rewriting it in logarithmic form. Give two forms for each answer: an exact expression and a calculator approximation rounded to three decimal places. Check to see that each result is consistent with the graphical estimate obtained in part (a). $$e^{t-1}=16$$

The age of some rocks can be estimated by measuring the ratio of the amounts of certain chemical elements within the rock. The method known as the rubidium-strontium method will be discussed here. This method has been used in dating the moon rocks brought back on the Apollo missions. Rubidium-87 is a radioactive substance with a half-life of \(4.7 \times 10^{10}\) years. Rubidium- 87 decays into the substance strontium- \(87,\) which is stable (nonradioactive). We are going to derive the following formula for the age of a rock: $$T=\frac{\ln \left[\left(\mathcal{N}_{s} / \mathcal{N}_{r}\right)+1\right]}{-k}$$ where \(T\) is the age of the rock, \(k\) is the decay constant for rubidium-87, \(\mathcal{N}_{s}\) is the number of atoms of strontium-87 now present in the rock, and \(\mathcal{N},\) is the number of atoms of rubidium-87 now present in the rock. (a) Assume that initially, when the rock was formed, there were \(\mathcal{N}_{0}\) atoms of rubidium-87 and none of strontium-87. Then, as time goes by, some of the rubidium atoms decay into strontium atoms, but the to tal number of atoms must still be \(\mathcal{N}_{0} .\) Thus, after \(T\) years, we have \(\mathcal{N}_{0}=\mathcal{N}_{r}+\mathcal{N}_{s}\) or, equivalently, $$ \mathcal{N}_{s}=\mathcal{N}_{0}-\mathcal{N}_{r}$$However, according to the law of exponential decay for the rubidium-87, we must have \(\mathcal{N}_{r}=\mathcal{N}_{0} e^{k T} .\) Solve this equation for \(\mathcal{N}_{0}\) and then use the result to eliminate \(\mathcal{N}_{0}\) from equation \((1) .\) Show that the result can be written $$\mathcal{N}_{s}=\mathcal{N}_{r} e^{-k T}-\mathcal{N}_{r}$$ (b) Solve equation (2) for \(T\) to obtain the formula given at the beginning of this exercise.

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