Chapter 11: Problem 27
Is \(y(x)=e^{3 x}\) the general solution of \(y^{\prime}=3 y ?\)
Short Answer
Expert verified
No, it's a particular solution; the general solution is \(y(x) = Ce^{3x}\).
Step by step solution
01
Differentiate the Given Function
First, let's find the derivative of the given function. The function is \(y(x) = e^{3x}\). Using the chain rule, differentiate \(y(x)\) with respect to \(x\). The derivative \(y'(x) = \frac{d}{dx}[e^{3x}] = 3e^{3x}\).
02
Compare with the Differential Equation
Now, compare the derivative \(y'(x) = 3e^{3x}\) from the previous step with the given differential equation \(y' = 3y\). Substitute the given function \(y = e^{3x}\) into the differential equation to get \(3y = 3e^{3x}\).
03
Verify Equality
Check if the expression \(3y = 3e^{3x}\) is equal to the derivative \(3e^{3x}\) obtained in Step 1. Since both sides are exactly equal, the function \(y(x) = e^{3x}\) satisfies the given differential equation.
04
Determine if it's the General Solution
For a solution to be a general solution, it must encompass all particular solutions and include an arbitrary constant. In this case, \(y(x) = e^{3x}\) does not include an arbitrary constant (e.g., \(C\)), so this function is only a particular solution and not the general solution. The general solution should be of the form \(y(x) = Ce^{3x}\) to include all possible integrals.
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
General Solution
In the context of differential equations, the general solution is a broader solution that includes all possible solutions to the differential equation. Consider a first-order differential equation of the form \(y' = 3y \). The general solution usually contains an arbitrary constant which signifies a family of solutions. This constant allows flexibility in solving for initial values or boundary conditions later on.
For example, a general solution might look like \(y(x) = Ce^{3x}\), where \(C\) is the arbitrary constant.
For example, a general solution might look like \(y(x) = Ce^{3x}\), where \(C\) is the arbitrary constant.
- The presence of \(C\) means that it encompasses every particular solution for different values of \(C\).
- Finding a general solution is an essential step, as it helps address more specific questions by using initial conditions to find particular solutions.
Particular Solution
A particular solution of a differential equation is one that is specific to an initial condition or boundary value. It is derived from the general solution by giving a specific value to the arbitrary constant.
Consider our function, \(y(x) = e^{3x}\). This is a particular solution to the differential equation \(y' = 3y\), resulting from setting the arbitrary constant \(C = 1\).
Consider our function, \(y(x) = e^{3x}\). This is a particular solution to the differential equation \(y' = 3y\), resulting from setting the arbitrary constant \(C = 1\).
- Particular solutions don't include an arbitrary constant, as they respond to specific initial values.
- Knowing at least one particular solution allows focusing on specific values for practical applications or problems.
Chain Rule
The Chain Rule is a fundamental concept in calculus used to differentiate composite functions. When a function is composed of two or more functions, the chain rule allows us to differentiate it efficiently.
In our original problem, the function \(y(x) = e^{3x}\) is differentiated using the chain rule. Here's how the rule works: if you have a composite function like \(e^{3x}\), the chain rule suggests taking the derivative of the outer function, \(e^u\), and multiplying it by the derivative of the inner function \(u = 3x\).
In our original problem, the function \(y(x) = e^{3x}\) is differentiated using the chain rule. Here's how the rule works: if you have a composite function like \(e^{3x}\), the chain rule suggests taking the derivative of the outer function, \(e^u\), and multiplying it by the derivative of the inner function \(u = 3x\).
- The derivative of \(e^{3x}\) is \(3e^{3x}\). This follows from: 1. The derivative of \(e^u\) is \(e^u\). 2. The derivative of \(3x\) is 3. Multiply these to get \(3e^{3x}\).
Exponential Function
Exponential functions are a crucial part of calculus and differential equations. They have the form \(f(x) = e^{kx}\), where \(e\) is the base of the natural logarithm, and \(k\) is a constant. These functions are unique because their derivatives are proportional to themselves. This property makes them important in solving differential equations.
In the given exercise, the function \(y(x) = e^{3x}\) serves as a typical example. Anytime a derivative of an exponential function is needed, the chain rule helps us find it, confirming their memorable nature:
In the given exercise, the function \(y(x) = e^{3x}\) serves as a typical example. Anytime a derivative of an exponential function is needed, the chain rule helps us find it, confirming their memorable nature:
- The function \(e^{3x}\) has a derivative \(3e^{3x}\), illustrating the self-proportional trait of exponential functions.
- This property is what allows exponential functions to model growth and decay processes.