Solving this Linear Differential Equation?

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Homework Help Overview

The discussion revolves around solving a linear differential equation of the form dy/dx + 18x^17y = x^18. Participants are exploring the use of integrating factors and integration techniques to find the general solution.

Discussion Character

  • Exploratory, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to solve the equation using integrating factors and expresses confusion about substituting the integral of e^{x^{18}} with a variable I. Other participants question the necessity of integrating e^{x^{18}} after already obtaining the integrating factor and suggest using integration by parts.

Discussion Status

The discussion is ongoing, with participants providing guidance on integration techniques and questioning the steps taken by the original poster. There is no explicit consensus, but various approaches are being explored.

Contextual Notes

Participants note that the online platform requires the use of the variable "I" in place of integral signs, which adds a layer of complexity to the problem. The original poster is seeking clarification on how to format their solution accordingly.

τheory
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Homework Statement


Find the general solution to this differential equation:
[itex]\frac{dy}{dx}+18x^{17}y=x^{18}[/itex]
Use the variable [itex]I[/itex] for replacing [itex]\int e^{x^{18}} dx[/itex]

2. The attempt at a solution
I've solved the differential equation using integrating factors and obtained the following result:
[itex]y=\frac{\int e^{x^{18}}x^{18} dx + C}{e^{x^{18}}}[/itex]

My problem is using the variable [itex]I[/itex] for replacing the [itex]\int e^{x^{{18}}} dx[/itex]. How am I suppose to do this with [itex]x^{18}[/itex] inside the integral?
 
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τheory said:

Homework Statement


Find the general solution to this differential equation:
[tex]\frac{dy}{dx}+18x^{17}y=x^{18}[/tex]Use the variable [itex]I[/itex] for replacing [itex]\int e^{x^{18}}\,dx[/itex]

2. The attempt at a solution
I've solved the differential equation using integrating factors and obtained the following result:
[tex]y=\frac{\int e^{x^{18}}x^{18}\,dx + C}{e^{x^{18}}}[/tex]My problem is using the variable [itex]I[/itex] for replacing the [itex]\int e^{x^{18}}\,dx[/itex]. How am I suppose to do this with x^18 inside the integral?
You can't. You want to integrate by parts now.
 
Are you familiar with the product rule?

(f*g)' = f'g + g'f

I am not following what you are doing at all...

You already got the integrating factor [tex]e^{x^18}[/tex], why do you have [tex]\int e^{x^18} dx[/tex]?
 
Okay well I did try using integration by parts after I obtained the general solution, but didn't get far as I got this:
[itex]\int e^{x^{18}}x^{18}dx[/itex]

[itex]u = x^{18}[/itex]
[itex]du = 18x^{17} dx[/itex]
[itex]dv = e^{x^{18}} dv[/itex]
[itex]v = \int e^{x^{18}} dv[/itex]

[itex]uv - \int v du[/itex]

[itex]x^{18}\int e^{x^{18}} dv - \int[ \int e^{x^{18}} dv] 18x^{17} dx[/itex]

At this point, how am I suppose to utilize the substitution of [itex]\int e^{x^{18}}dx[/itex] with [itex]I[/itex]? In other words, how do I input the general solution into the website without inputting integrals? Since the website doesn't recognize integral signs, which is why it's asking me to use [itex]I[/itex] for every [itex]\int e^{x^{18}}dx[/itex] I encounter.

To the flyingpig's question, I need to use the variable "I" because it says to do so in the online problem that I'm doing.
 
Try using u=x and [itex]dv=x^{17}e^{x^{18}}\,dx[/itex].
 

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