Find integrating factor and solve the equation

In summary, the conversation discusses the use of an integrating factor in solving a differential equation. The person initially multiplied the equation by the integrating factor, but after experiencing difficulty, they were advised to divide by it instead. This led to success in solving the equation. The person also notes that they had always been taught to multiply by the integrating factor, but now realize that dividing can also be effective.
  • #1
naspek
181
0
y dx + x ln x dy = 0 ; x > 0


my integrating factor is x..


so.. multiply with DE,


xy dx + x^2 ln x dy = 0


let M = xy ; N = x^2 ln x


dM/dy = x ; dN/dx = x + 2x ln x


the problem is.. i didn't get the exact equation after multiply the integrating factor.. I've double checked my integrating factor.. but.. still can't get the exact equation...
 
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  • #2
Try dividing by x instead.
 
  • #3
vela said:
Try dividing by x instead.
which part?
 
  • #4
Instead of multiplying the equation by your integration factor, divide by it instead.
 
  • #5
vela said:
Instead of multiplying the equation by your integration factor, divide by it instead.
wow! i got it! but.. i never divide DE by integrating factor..
always multiply..
 

What is an integrating factor?

An integrating factor is a function that is used to multiply a differential equation in order to make it easier to solve. It is usually used when the equation is not in a standard form and needs to be put in a more manageable form.

How do you find an integrating factor?

To find an integrating factor, you need to first identify the type of differential equation you are dealing with. Depending on the type, there are different methods to find the integrating factor. For example, for a linear differential equation, the integrating factor can be found by dividing the coefficients of the dependent variable. For a non-linear differential equation, you may need to use a substitution or a specific formula to find the integrating factor.

What is the purpose of finding an integrating factor?

The purpose of finding an integrating factor is to make it easier to solve a differential equation. By multiplying the equation with the integrating factor, you can transform a non-linear or non-standard equation into a linear or standard form, which can be solved using known methods or techniques.

How do you solve a differential equation using an integrating factor?

Once you have found the integrating factor, you can use it to multiply the entire differential equation. This will transform the equation into a linear form, which can be solved using standard techniques such as separation of variables or the method of undetermined coefficients. After solving the equation, you can then use the integrating factor to find the solution to the original equation.

Can all differential equations be solved using an integrating factor?

No, not all differential equations can be solved using an integrating factor. It is most commonly used for first-order linear or non-linear equations. However, higher-order equations or equations with certain types of coefficients may not be suitable for solving using an integrating factor. In these cases, other methods or techniques may need to be used.

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