Solving an ODE by the method of Integrating Factors

In summary, the conversation discusses solving an ODE involving a function of both x and y using the method of integrating factors. The problem is initially challenging due to the presence of y in the function, but can be solved by dividing by y^2/3 and using the derivative of y^(1/3). Eventually, the solution involves simplifying the right-hand side to a form that can be integrated.
  • #1
1missing
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1. y' + y = x y2/32. The problem states we need to solve this ODE by using the method of integrating factors. Every example I found on the internet involving this method was of the form:

y' + Py = Q

Where P and Q are functions of x only. In the problem I was given however, Q is a function of both x and y. If I try to proceed with the method I end up with:

(d/dx) ex y = x ex y2/3


Annnnd that's where I'm stuck. Am I missing something here or was this problem incorrectly assigned?
 
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  • #2
So what do you have to do to make the right-hand side a function in ##x## only ?
 
  • #3
Divide by y2/3 on both sides of the original equation, but then I've got a term in front of the y' and that doesn't seem to get me closer to a solution.
 
  • #4
What is ##\frac{d(y^{1/3})}{dx}## equal to?
 
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Likes Delta2
  • #5
Son of a...I probably would've stared at this thing for a couple of days before I noticed that. That should get me to a solution, let me give it a go.
 
  • #6
1missing said:
I end up with:
(d/dx) ex y = x ex y2/3

Annnnd that's where I'm stuck. Am I missing something here or was this problem incorrectly assigned?
You could also proceed by noting that the righthand side is equal to ##x e^{x/3} (e^x y)^{2/3}##.
 

1. What is an ODE and why is it important to solve it?

An ODE, or Ordinary Differential Equation, is a mathematical equation that describes how a dependent variable changes with respect to an independent variable. It is important to solve ODEs because they are used to model many real-world processes in physics, engineering, economics, and other fields.

2. What is the method of integrating factors?

The method of integrating factors is a technique used to solve certain types of ODEs. It involves multiplying both sides of the equation by an integrating factor, which is a function that helps to simplify the equation and make it easier to solve.

3. How do you determine the integrating factor?

The integrating factor for an ODE can be determined by multiplying the coefficient of the dependent variable by the derivative of the independent variable, and then integrating this expression. Alternatively, there are tables and formulas available for determining the integrating factor for specific types of ODEs.

4. Can the method of integrating factors be used for all ODEs?

No, the method of integrating factors is only applicable to certain types of ODEs, specifically first-order linear ODEs. It cannot be used for nonlinear or higher-order ODEs.

5. Are there any limitations to using the method of integrating factors?

One limitation of the method of integrating factors is that it can only be used for ODEs with constant coefficients. Additionally, it may not always be the most efficient method for solving ODEs, and other techniques such as separation of variables or substitution may be more appropriate.

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