Can someone help me i don't understand this DE

  • Thread starter iScience
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In summary, the conversation discusses solving the problem xy''-4y'=x^4 and determining the general solution and particular solution. While the speaker's solution includes the term -(1/25)x^5, the correct answer is simply (1/5)lnx(x^5). The conversation also mentions that in general, the homogeneous solution should not be included in the particular solution when finding the general solution of an ODE.
  • #1
iScience
466
5
problem: xy''-4y'=x^4

when i solve it i get y(homogeneous)=C1+C2x^5 which is fine because that's what the back of the book says

but for the particular solution, i get .. C1=-(1/25)x^5 , C2=(1/5)lnx

so y(general)= C1+C2x^5-(1/25)x^5+(1/5)lnx(x^5)

but wolframalpha as well as the back of my book both say the answer is...
y(general)=C1+C2x^5+(1/5)lnx(x^5)

where does the -(1/25)x^5 term go?...
 
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  • #2
You have
C1 x5 + C2 x5 = C3x5

Does that help?
 
Last edited:
  • #3
so technically my answer is correct and they just combined the x^5 terms.. i see
 
  • #4
Thanks!
 
  • #5
If you're finding the general solution of an ODE, then usually you would not allow pieces of the homogeneous solution to show up in the particular solution.
 

FAQ: Can someone help me i don't understand this DE

What is a DE?

A DE, or differential equation, is a mathematical equation that describes the relationship between a function and its derivatives. It is commonly used in the field of science to model various natural phenomena.

Why is it important to understand DE?

Understanding DE is important because it allows us to accurately model and predict the behavior of many systems in the natural world. This can help us make informed decisions and develop new technologies.

What are some common applications of DE?

DE has a wide range of applications in various fields such as physics, engineering, biology, economics, and more. It is used to model systems such as population growth, chemical reactions, electric circuits, and fluid dynamics.

What are the different types of DE?

There are two main types of DE: ordinary differential equations (ODEs) and partial differential equations (PDEs). ODEs involve a single independent variable, while PDEs involve multiple independent variables.

How can I learn more about DE?

There are many resources available to help you understand DE, such as textbooks, online tutorials, and courses. It is also helpful to practice solving different types of DE problems to improve your understanding. Seeking guidance from a teacher or mentor can also be beneficial.

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