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Find particular solutions. $$\frac{d B}{d t}+0.1 B-10=0 \quad B(2)=3$$

Short Answer

Expert verified
The particular solution is \( B(t) = -97e^{0.2 - 0.1t} + 100 \).

Step by step solution

01

Recognize the Form of the Differential Equation

The given differential equation is of the form \( \frac{dB}{dt} + pB = q \). In this equation, \( p = 0.1 \) and \( q = 10 \). This indicates it is a first-order linear differential equation.
02

Solve the Homogeneous Equation

First, solve the homogeneous equation \( \frac{dB}{dt} + 0.1B = 0 \). By separation of variables or recognizing the standard form, the solution is \( B_h(t) = Ce^{-0.1t} \), where \( C \) is a constant.
03

Find a Particular Solution of the Non-Homogeneous Equation

To find a particular solution, assume a constant solution \( B_p = k \). Substitute \( B_p = k \) into the non-homogeneous equation: \( 0.1k - 10 = 0 \). Solving for \( k \) gives \( k = 100 \). Hence, the particular solution is \( B_p(t) = 100 \).
04

General Solution

Combine the homogeneous solution \( B_h(t) = Ce^{-0.1t} \) with the particular solution \( B_p(t) = 100 \): \( B(t) = Ce^{-0.1t} + 100 \).
05

Use Initial Condition to Find the Constant

Apply the initial condition \( B(2) = 3 \). Substitute into the general solution: \( 3 = Ce^{-0.1(2)} + 100 \). Simplifying, \( 3 = Ce^{-0.2} + 100 \). Thus, \( Ce^{-0.2} = -97 \). Solve for \( C \): \( C = -97e^{0.2} \).
06

Particular Solution with Specific Initial Condition

Substitute \( C = -97e^{0.2} \) back into the general solution: \( B(t) = -97e^{0.2} e^{-0.1t} + 100 \), which simplifies to \( B(t) = -97e^{0.2 - 0.1t} + 100 \).

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Key Concepts

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

First-Order Linear Differential Equations
Differential equations are equations involving derivatives of a function. A first-order linear differential equation is a specific type of these equations. It involves the first derivative of a function and has the standard form \( \frac{dy}{dx} + p(x)y = q(x) \). - Here, \( y \) is the function we’re trying to find.- \( p(x) \) and \( q(x) \) are functions of the independent variable. In the exercise, our equation is \( \frac{dB}{dt} + 0.1B = 10 \), making it a first-order linear differential equation since it includes the first derivative \( \frac{dB}{dt} \) and a constant coefficient \( 0.1 \).The goal with such equations is to find a general solution that satisfies it. This is often done by combining the solutions of the corresponding homogeneous equation and a particular solution.
Particular Solution
A particular solution addresses only one part of the differential equation problem at hand. It's a specific solution derived from the non-homogeneous counterpart of the original differential equation.- For our equation, the non-homogeneous differential equation is \( \frac{dB}{dt} + 0.1B = 10 \).- To find a particular solution, you usually guess a form based on \( q(x) \) or set coefficients to solve In this exercise, by setting \( B_p = k \), we assume that our particular solution is a constant. When substituting, we get \( 0.1k = 10 \), giving us \( k = 100 \).Thus, our particular solution is \( B_p(t) = 100 \).Particular solutions provide a specific example that satisfies the differential equation.
Homogeneous Equation
A homogeneous equation is derived from removing the non-homogeneous part (i.e., \( q(x) \)) of our differential equation. This involves considering\( \frac{dB}{dt} + 0.1B = 0 \).Solutions to this are critical, as they form part of the general solution when combined with the particular solution. Using various methods like separation of variables, the homogeneous solution is often exponential.For our equation, solving gives us \( B_h(t) = Ce^{-0.1t} \), where \( C \) is an arbitrary constant.The form involves exponential functions that decay or grow depending on the signs and values of the coefficients. This aspect allows you to adjust the solution to fit various initial conditions.
Initial Condition
Initial conditions allow us to find the specific solution that not only satisfies the differential equation but also meets given criteria at specific points.- In our example, the initial condition is \( B(2) = 3 \).By substituting in the general equation, \( B(t) = Ce^{-0.1t} + 100 \),we solve for \( C \):\( 3 = Ce^{-0.2} + 100 \), leading to \( Ce^{-0.2} = -97 \).Solving this, we find \( C = -97e^{0.2} \).This shows how initial conditions personalize a solution, ensuring that it meets particular criteria at a given point. This step is crucial when applying mathematics to real-world contexts where specific measurements or data points are known.

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Most popular questions from this chapter

Create a system of differential equations to model the situations. You may assume that all constants of proportionality are 1. A population of fleas is represented by \(x,\) and a population of dogs is represented by \(y .\) The fleas need the dogs in order to survive. The dog population, however, is unaffected by the fleas.

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Alcohol is metabolized and excreted from the body at a rate of about one ounce of alcohol every hour. If some alcohol is consumed, write a differential equation for the amount of alcohol, \(A\) (in ounces), remaining in the body as a function of \(t,\) the number of hours since the alcohol was consumed.

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