Chapter 3: Problem 17
If the Wronskian
Short Answer
Expert verified
Question: Determine the function g(t) given that the Wronskian W of the functions f(t) and g(t) is 3e^(4t) and the function f(t) is e^(2t).
Answer: g(t) = 3te^(2t) + Ce^(2t), where C is an arbitrary constant.
Step by step solution
01
Write down the given information
We are given the following:
- Wronskian,
- Function
Our task is to find the function .
02
Compute the derivative of
In order to use the Wronskian formula, we need to find the derivative of . Differentiating with respect to , we get:
03
Write down the Wronskian formula and substitute the given information
We know that the Wronskian is given by the formula:
Substitute the given information into the formula:
04
Solve the differential equation for
Now, we need to solve the differential equation for . This is a first-order linear inhomogeneous differential equation. Let's first divide through by :
Simplify the equation:
Let's write it in the form of a first-order linear differential equation:
05
Use the integrating factor method to solve the differential equation
We can solve this differential equation using the integrating factor method. First, we calculate the integrating factor ( ):
Now, multiply both sides of the differential equation by the integrating factor:
This simplifies to:
Now, integrate both sides with respect to :
This gives:
Now, multiply both sides by the integrating factor's inverse, which is :
Here, is the function we were looking for, and is an arbitrary constant.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Differential Equations
A differential equation is a mathematical equation that involves functions and their derivatives. These equations can describe various phenomena such as growth, decay, oscillation, and waves. Differential equations are categorized based on the order of the highest derivative and whether they are linear or non-linear.
- The **order** of a differential equation is determined by the highest derivative present. For example, a second-order differential equation has the second derivative but not higher.
- A **linear** differential equation has solutions that form a straight line, while non-linear ones do not.
Integrating Factor
The integrating factor is a mathematical tool used to solve linear differential equations. This method is particularly useful for equations that are not directly integrable.
, calculated from the given differential equation . Multiplying the entire equation by this factor transforms it, making it easier to solve.
- To find the integrating factor (
, we calculate where is the function multiplying in . - The goal of the integrating factor is to turn the differential equation into an exact differential, which can then be integrated straightforwardly.
Inhomogeneous Differential Equation
An **inhomogeneous differential equation** is one that contains a non-zero term independent of the function being solved for. This term is called the forcing function or non-homogeneous term and adds extra complexity to the equation.
is the non-homogeneous part, requiring special methods like the integrating factor to find a complete solution.
- A simple form of an inhomogeneous differential equation looks like
, where is not equal to zero. - Finding solutions often involves both a complementary (homogeneous) solution and a particular solution that addresses the non-homogeneous part.
Function Derivation
Function derivation is the process of finding the derivative of a function, which measures how the function changes as its input changes. The derivative is a fundamental concept in calculus and is symbolized by or .
leads to , which is essential for applying the Wronskian and solving the differential equation for . Function derivation allows for a more in-depth analysis of how functions behave and interact over different values of .
- Derivatives are used to determine slopes of curves, rates of change, and to solve differential equations.
- The process involves rules and techniques such as the product rule, chain rule, and power rule.