Integration Factors: Solving Problems

In summary, the first problem can be solved by trying different assumptions for the integrating factor and finding it by solving a differential equation. The second problem can be solved by modifying the equation to make it possible to find the integrating factor, resulting in the solutions of y^3e^x+ye^(2x)=c and ln(x^2 + y^2) +2y - 2x = c.
  • #1
confusedM
7
0
I am having issues finding the integration factor for the following two problems. I believe the second one can be solved by inspection.

1. (y^3+2ye^x)dx + (e^x+3y^2)dy = 0


2. (x-x^2-y^2)dx + (y+x^2+y^2)dy = 0
 
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  • #2
For the first one, try assuming in turn that the integrating factor is a function of either x or y only, then see if you can come up with it by solving a DE.

What do you mean by 2nd one being solvable by inspection?
 
  • #3
I tried using the method described by the book. Setting M= y^3+2ye^x and N = (e^x+3y^2)... then taking dM/dy and dN/dx... then (dM/dy - dN/dx) / N and (dN/dx - dM/dy) / M... I don't know if my problem is that I did something wrong in the derivations but neither gives me an integration factor that is a function of just y or just x.

As far as the second goes, I meant that the equation needs to be modified so that the above is possible (dM/dy = dN/dx), but I can't figure out how to modify the equation around so that is possible.

The solutions are supposed to be:
1. y^3e^x+ye^(2x)=c
2. ln(x^2 + y^2) +2y - 2x = c
 
  • #4
never mind. I got it.
 

Related to Integration Factors: Solving Problems

What are integration factors?

Integration factors are mathematical tools used in solving differential equations. They are constants that can be multiplied to a differential equation to convert it into an exact differential equation, making it easier to solve.

Why are integration factors important?

Integration factors are important because they help simplify the process of solving differential equations. They allow us to convert non-exact differential equations into exact ones, which can then be solved using basic integration techniques.

How do you find an integration factor?

To find an integration factor, you need to follow a specific formula based on the type of differential equation you are solving. For linear differential equations, the integration factor is e^(integral of coefficient of y dx). For non-linear equations, the integration factor is e^(integral of P(x) dx), where P(x) is the coefficient of y.

What are some common applications of integration factors?

Integration factors are commonly used in physics, engineering, and other fields that involve modeling and solving differential equations. They are also used in economic and financial analysis, as well as in population dynamics and biology.

Can integration factors be used to solve any differential equation?

No, integration factors can only be used to solve certain types of differential equations, specifically those that can be converted into exact differential equations. Non-linear equations with non-constant coefficients may not have an integration factor and therefore cannot be solved using this method.

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