Chapter 1: Problem 27
Find explicit particular solutions of the initial value problems in Problems 19 through \(28.\) $$ \frac{d y}{d x}=6 e^{2 x-y}, \quad y(0)=0 $$
Short Answer
Expert verified
The particular solution is \( y = \ln(3e^{2x} - 2) \).
Step by step solution
01
Set up the differential equation
We are given the differential equation \( \frac{d y}{d x}=6 e^{2 x-y} \) with the initial condition \( y(0)=0 \). The goal is to find the particular solution that satisfies this condition.
02
Separate the variables
To separate the variables, we rearrange the terms to get \( e^y \frac{d y}{d x} = 6 e^{2x} \). Then we rearrange to isolate variables: \( e^y \, dy = 6 e^{2x} \, dx \).
03
Integrate both sides
Integrate both sides of the equation: \( \int e^y \, dy = \int 6 e^{2x} \, dx \). The integrals are \( e^y = C \) and \( \frac{6}{2}e^{2x} = 3e^{2x} + C \).
04
Solve the integral equation
After integration, we equate them to get \( e^y = 3e^{2x} + C \). We need to solve this equation for \( y \): \( y = \ln(3e^{2x} + C) \).
05
Apply the initial condition
Substitute the initial condition \( y(0) = 0 \) into the solution: \( 0 = \ln(3e^{2 \cdot 0} + C) \), which simplifies to \( 0 = \ln(3 + C) \). Solving \( e^0 = 3 + C \) gives \( C = -2 \).
06
Write the particular solution
Substitute \( C = -2 \) back into the general solution to get the particular solution: \( y = \ln(3e^{2x} - 2) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Initial Value Problem
An Initial Value Problem (IVP) is a differential equation that comes with a specific condition provided at a certain point. In this type of problem, you are given a differential equation and an initial condition that the solution must satisfy. This initial condition often involves specifying the value of the unknown function at a particular point.
### How It Works- **Differential Equation**: This is the equation involving derivatives, representing rates of change. In our example, the differential equation is \( \frac{d y}{d x}=6 e^{2 x-y} \).- **Initial Condition**: This is typically given as \( y(x_0)=y_0 \). In the problem above, we have \( y(0)=0 \). The purpose of an IVP is to narrow down the possibilities among the infinite number of solutions that a general differential equation might have. By applying this condition, we find a unique solution that exactly fits the initial scenario described by the problem.
### How It Works- **Differential Equation**: This is the equation involving derivatives, representing rates of change. In our example, the differential equation is \( \frac{d y}{d x}=6 e^{2 x-y} \).- **Initial Condition**: This is typically given as \( y(x_0)=y_0 \). In the problem above, we have \( y(0)=0 \). The purpose of an IVP is to narrow down the possibilities among the infinite number of solutions that a general differential equation might have. By applying this condition, we find a unique solution that exactly fits the initial scenario described by the problem.
Separation of Variables
Separation of variables is a crucial technique used to solve differential equations, particularly when we deal with an equation involving a derivative equal to the product of two functions. ### The TechniqueThis method involves rearranging the equation so that each variable and its differential can be isolated on opposite sides of the equation. By doing so, you separate \( y \) and \( x \) to facilitate integration.
In our exercise, we took the equation \( \frac{d y}{d x} = 6 e^{2 x-y} \) and transformed it by moving all \( y \)-terms to one side and all \( x \)-terms to the other side: - From \( e^y \frac{d y}{d x} = 6 e^{2x} \)- To \( e^y \, dy = 6 e^{2x} \, dx \)This crucial step allows the integration of both sides independently, leading us closer to solving the problem.
In our exercise, we took the equation \( \frac{d y}{d x} = 6 e^{2 x-y} \) and transformed it by moving all \( y \)-terms to one side and all \( x \)-terms to the other side: - From \( e^y \frac{d y}{d x} = 6 e^{2x} \)- To \( e^y \, dy = 6 e^{2x} \, dx \)This crucial step allows the integration of both sides independently, leading us closer to solving the problem.
Particular Solution
Finding a particular solution involves determining a specific solution to a differential equation that also satisfies an initial condition. After integrating using the separation of variables, we generally end up with a general solution containing a constant, \( C \).
### Applying the Initial ConditionTo find the particular solution:- Solve the equation \( e^y = 3e^{2x} + C \), acquired in our step-by-step solution.- Substitute the initial condition \( y(0)=0 \) into the solution.- This results in \( 0 = \ln(3 \cdot e^{0} + C) \) translating to \( 0 = \ln(3 + C) \).- Solve for \( C \), obtaining \( C = -2 \).The particular solution that meets the initial condition is therefore \( y = \ln(3e^{2x} - 2) \), a tailored solution fitting every requirement outlined by the initial value problem.
### Applying the Initial ConditionTo find the particular solution:- Solve the equation \( e^y = 3e^{2x} + C \), acquired in our step-by-step solution.- Substitute the initial condition \( y(0)=0 \) into the solution.- This results in \( 0 = \ln(3 \cdot e^{0} + C) \) translating to \( 0 = \ln(3 + C) \).- Solve for \( C \), obtaining \( C = -2 \).The particular solution that meets the initial condition is therefore \( y = \ln(3e^{2x} - 2) \), a tailored solution fitting every requirement outlined by the initial value problem.