Can homogeneous substitution solve this differential equation?

In summary, the conversation is about solving a differential equation involving the derivative of y with respect to x. The solution involves using basic algebra to rewrite the equation in a simpler form, using the fact that √(xy + x^2)/x is equivalent to √[(xy + x^2)/x^2]. The person asking for help was able to understand the solution with this explanation.
  • #1
jdawg
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Homework Statement


x(dy/dx) - y = sqrt(xy +x2)

Homework Equations

The Attempt at a Solution


I got up to this point: u=y/x

dy/dx = (sqrt(xy+x2))/x + y/x

And then the solution shows this:

dy/dx = y/x + (y/x+1)½

Please help, I don't understand how they got to that point.
 
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  • #2
Also, sorry about the bad formatting. Where did they move the square root symbol and fraction symbol?
 
  • #3
It's fairly elementary algebra that was probably dinned into you at some point and you have forgotten.

√(xy + x2)/x = √(xy + x2)/√((x2) = √[(xy + x2)/x2] = ...

You might last time have lost sight of the why, just drilled to do that: hope something comes back but this time instead look to see how it makes sense.
 
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  • #4
Thank you so much! Haha its been a minute since I've had algebra. Great explanation! :D
 

What is a homogeneous substitution DE?

A homogeneous substitution differential equation (DE) is a type of differential equation where all the terms can be written in terms of a single variable, typically denoted by u or v. This substitution allows for the equation to be simplified and solved more easily.

How is a homogeneous substitution DE solved?

To solve a homogeneous substitution DE, the substitution variable (u or v) is substituted into the equation to create a new equation with only one variable. This new equation can then be solved using standard methods, such as separation of variables or integrating factors.

What is the purpose of using a homogeneous substitution in DEs?

The purpose of using a homogeneous substitution in DEs is to simplify the equation and make it easier to solve. It allows for the equation to be expressed in terms of a single variable, which can then be solved using standard techniques and methods.

Can all DEs be solved using a homogeneous substitution?

No, not all DEs can be solved using a homogeneous substitution. This method is only applicable to certain types of differential equations, specifically those that can be written in terms of a single variable. Other methods, such as the method of undetermined coefficients or variation of parameters, may be needed to solve other types of DEs.

Are there any limitations to using a homogeneous substitution in DEs?

Yes, there are limitations to using a homogeneous substitution in DEs. This method is only applicable to linear differential equations, meaning the dependent variable and its derivatives are raised to the first power. It also cannot be used for DEs with constant coefficients or non-homogeneous terms.

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