Name: exponential growth and decay models
Uploaded: 2025-11-26T05:43:46.000Z
Duration: 1 min 29 s
Channel: JoVE

Uma função exponencial é definida por uma base positiva - não igual a um - elevada a um expoente de número real.Sua forma geral é um valor inicial multiplicado pela base elevada a um expoente.Quando a base é maior que um, a função modela o crescimento. Quando está entre zero e um, de forma não inclusiva, modela o decaimento.Por exemplo, considere uma droga que atinge uma concentração inicial de 30 microgramas por mililitro na corrente sanguínea após a injeção e retém 75% de sua concentração a cada hora.Nesse caso, a função exponencial é 30 multiplicada por 0,75 elevada ao expoente t, representando as horas passadas.Após uma hora, a concentração cai para 22,5 microgramas por mililitro. Depois de duas horas, torna-se 16,9 microgramas por mililitro e o padrão continua.Em um gráfico, a curva cai rapidamente no início, depois se achata gradualmente, aproximando-se de uma assíntota horizontal em zero.Como o tempo não pode ser negativo, o domínio são os números reais não negativos. Como a concentração nunca chega a zero, o intervalo inclui apenas valores positivos.

introdução às funções exponenciais

As fun&#231;&#245;es exponenciais s&#227;o fundamentais na modelagem de processos din&#226;micos nos quais a taxa de varia&#231;&#227;o &#233; proporcional ao valor atual. Definidas por f(x) = b^x, onde b &#233; uma constante positiva diferente de um, elas formam a base para descrever processos de crescimento e decaimento, dependendo de se a base b &#233; maior ou menor que um.Modelos exponenciais descrevem situa&#231;&#245;es em que a varia&#231;&#227;o ocorre a uma taxa proporcional &#224; quantidade atual. Isso inclui fen&#244;menos como prolifera&#231;&#227;o bacteriana, decaimento de subst&#226;ncias radioativas e deprecia&#231;&#227;o de ativos. A forma geral de um modelo exponencial pode ser expressa por:<figure class='image image-style-align-center image_resized' style='display:table;margin-left:auto;margin-right:auto;width:75%;'><img style='aspect-ratio:1920/84;' src='https://cloudfront.jove.com/files/ftp_upload/40061/40061_Equation_1_editor_40061.svg' alt='40061_Equation_1.svg' /></figure>Aqui, A_0 &#233; a quantidade inicial, b &#233; a base que indica o fator de crescimento (b &gt; 1) ou decaimento (0 &lt; b &lt; 1) e t representa o tempo ou outra vari&#225;vel cont&#237;nua.Transforma&#231;&#245;es como transla&#231;&#245;es, reflex&#245;es e alongamentos alteram a representa&#231;&#227;o gr&#225;fica das fun&#231;&#245;es exponenciais, mas preservam sua forma fundamental e o comportamento assint&#243;tico. Al&#233;m disso, a Propriedade injetora das fun&#231;&#245;es exponenciais garante que, se b^x = b^y, ent&#227;o x = y, permitindo resolver equa&#231;&#245;es envolvendo expoentes por meio de compara&#231;&#227;o de bases.

Introdução às Funções Exponenciais

As fun&#231;&#245;es exponenciais s&#227;o fundamentais na modelagem de processos din&#226;micos nos quais a taxa de varia&#231;&#227;o &#233; ...

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JoVE Core

Math Fundamentals

Fundamentos da Matemática

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Exponential and Logarithmic Functions

Funções Exponenciais e Logarítmicas

KEY TERMS AND CONCEPTS

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Introduction to Exponential Functions

exponential growth and decay models

Exponential functions model growth and decay when the rate of change depends on the current value. They are written as f(x) = b^x, where b is a positive constant and not equal to 1. When the base b is greater than 1, the function shows growth. When 0 &lt; b &lt; 1, the function shows decay.

These models are useful in many real situations. They can describe bacterial proliferation, radioactive substance decay, and the depreciation of assets. In each case, the change is proportional to the current amount. A general exponential model can be written as A₀b^t, where A₀ is the initial amount, b is the growth or decay factor, and t is time or another continuous variable.

Exponential graphs can also be changed with transformations. Translations, reflections, and stretches shift or reshape the graph, but the basic curve and asymptotic behavior stay the same. Exponential functions also have the One-to-One Property. If b^x = b^y, then x = y, which lets you solve equations with exponents by comparing the bases.

Exponential Growth and Decay Models

introduction to exponential functions

Exponential functions model growth and decay when the rate of change depends on the current value. They are written as f(x) = b^x, where b is a positive constant and not equal to 1. When the base b is greater than 1, the function shows growth. When 0 &lt; b &lt; 1, the function shows decay. These models are useful in many real situations. They can describe bacterial proliferation, radioactive substance decay, and the depreciation of assets. In each case, the change is proportional to the...

exponential functions with base e

Exponential Growth and Decay in Real Life

Exponential functions with base e model continuous growth and decay in real life. The constant e is about 2.718. It appears naturally when change depends on the current value. A positive exponent shows continuous growth, while a negative exponent shows continuous decay. These functions are useful when change happens smoothly over time instead of in steps. One example of exponential decay is a hot beverage cooling down. The temperature drops quickly at first. As it gets closer to room...

introduction to logarithmic functions

Logarithms as Exponents Reversed

Logarithmic functions are the inverse of exponential functions. They are used to solve for exponents. In the general form y = log_a(x), the base a must be greater than 0 and not equal to 1. A logarithm tells you the power needed to get a given number. In other words, y = log_a(x) gives the exponent that the base a must be raised to in order to obtain x. The function is defined only for x &gt; 0, but its range includes all real numbers. The graphs of logarithmic and exponential functions are...

laws of logarithms i

Logarithm Rules for Product and Quotient

Logarithm rules help simplify expressions that use powers, multiplication, and division. A logarithm is the inverse of exponentiation, so it shows how many times a base must be raised to reach a number. For base 10, the common logarithm is written as log. If 10^n = x, then log(x) = n. These rules are useful because they turn harder calculations into simpler steps. The product law says that the logarithm of a product equals the sum of the logarithms. For example, log(100) can be rewritten as...

laws of logarithms ii

Power Law and Change-of-Base Formula

Logarithmic laws help simplify exponential expressions and make them easier to evaluate. Two key tools are the power law and the change-of-base formula. These rules are useful in math and in applied settings where powers and repeated multiplication appear often. The power law says that the logarithm of a number raised to an exponent equals the exponent multiplied by the logarithm of the number. This rule is helpful when solving equations that involve growth over time, such as compound interest.

exponential equations with logarithms: problem solving

exponential-equations-with-logarithms-problem-solving

Solving Population Growth with Logarithms

Logarithms help solve population growth problems with exponential models. In ecology, these models are used to predict how a population changes over time when conditions stay favorable. The growth rate is proportional to the current population, so the number increases in a continuous and compounding way. The model writes population as a function of time. It combines the initial population with a growth factor raised to an exponent that includes the growth rate and the time. To find when a...

applications of logarithms

Logarithms in Sound and Decibels

Logarithms help describe sound intensity with the decibel scale. They are useful when a quantity changes over a very wide range. In acoustics, the decibel (dB) scale turns sound levels into numbers that are easier to compare and use. Sound can range from a faint whisper to the roar of a jet engine. A linear scale would make those differences hard to manage. The decibel scale is a logarithmic scale, which means it measures sound intensity level relative to a reference value. For air, that...

exponential equations for modeling growth

exponential-equations-for-modeling-growth

Exponential Growth in Population Models

Exponential growth in population models describes rapid, multiplicative change. It is useful when a population grows by the same factor at regular intervals. This makes it a strong fit for early-stage growth in natural systems. A bacterial culture that doubles every three hours can be modeled with an exponential equation. The model is n(t)=n0·2^(t/3), where n(t) is the population at time t and n0 is the starting population. The base 2 matches the doubling pattern. A more general exponential...

key terms and concepts

Explore exponential growth and decay models, graph transformations, real-world examples like bacteria and radioactive decay, and the one-to-one property.

Exponential Growth and Decay Models | JoVE K12

The JoVE Math Fundamentals collection is designed to build a deep and comprehensive understanding of essential mathematics. Covering the foundations of algebra, geometry, trigonometry, and analytic reasoning, this course establishes a strong base for future studies. The collection connects core mathematical concepts with real-world practice, equipping learners to solve complex problems, master problem-solving skills, and apply abstract ideas.

math fundamentals

Exponential Growth and Decay Models

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