Integrating Factor: Need Help Solving Excersice?

In summary, the conversation involves discussing the use of an integrating factor, N, to solve a differential equation. The speaker is unsure if their approach is correct and is seeking help in understanding if their calculation proves the statement that N*f(S) is also an integrating factor. The conversation also touches on the introduction of variables such as q, dx, and dy, and the concept of an exact differential equation.
  • #1
B4cklfip
18
0
Homework Statement
Show that if N is an integrating factor also N*f(S) is an integrating factor.
Relevant Equations
##dS = \frac{dU+pdV}{N}##
I'm not sure if that is the right way to solve this excersice. Can someone maybe help and tell me if this calculation proofs the statement ?

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  • #2
B4cklfip said:
Homework Statement:: Show that if N is an integrating factor also N*f(S) is an integrating factor.
Relevant Equations:: ##dS = \frac{dU+pdV}{N}##

I'm not sure if that is the right way to solve this excersice. Can someone maybe help and tell me if this calculation proofs the statement ?

View attachment 263972
First off, ending with 0 = 0 doesn't do you any good.
Second, I'm having a hard time trying to follow what you're doing. Why are you introducing q in the 2nd line and dx and dy in the 3rd line?
What is the differential equation you're trying to solve? Is it Udx + Vdy = 0?
You are given that N is an integrating factor. How have you used it? The basic idea is that U(x, y)dx + V(x, y)dy = 0 is not an exact differential equation, multiplying by an integrating factor causes the new equation to be exact.
 

What is the purpose of integrating factor in solving exercises?

The purpose of integrating factor is to simplify differential equations by multiplying both sides of the equation by a function that transforms the equation into a form that is easier to solve.

How do I determine the integrating factor for a given differential equation?

The integrating factor can be determined by finding the function that makes the left side of the equation equal to the derivative of the product of the integrating factor and the original equation.

What are the steps for using integrating factor to solve a differential equation?

The steps for using integrating factor to solve a differential equation are:
1. Identify the differential equation and determine if it is in the correct form for integrating factor.
2. Find the integrating factor by using the method mentioned in the previous question.
3. Multiply both sides of the equation by the integrating factor.
4. Simplify the equation and solve for the variable.
5. Check your solution by plugging it back into the original equation.

Can integrating factor be used for all types of differential equations?

No, integrating factor can only be used for linear first-order differential equations. It cannot be used for higher-order differential equations or non-linear differential equations.

What are some common mistakes to avoid when using integrating factor to solve a differential equation?

Some common mistakes to avoid when using integrating factor are:
- Forgetting to multiply both sides of the equation by the integrating factor.
- Making a mistake when finding the integrating factor.
- Not simplifying the equation after multiplying by the integrating factor.
- Forgetting to check the solution by plugging it back into the original equation.
- Using integrating factor for a differential equation that is not in the correct form.

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