General Solution for y''+(1/x)y'=0: Proving Boundedness

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Homework Help Overview

The discussion revolves around finding the general solution to the differential equation y''+(1/x)y'=0 and demonstrating that only constant solutions are bounded. Participants also explore a related question regarding the continuity of solutions for the equation y''=0.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to find the general solution using an integrating factor and integrates the resulting expressions. Some participants question the boundedness of the solutions, particularly noting that ln(x) is unbounded. Others raise a similar question regarding the continuity of solutions for a different equation.

Discussion Status

Participants are actively discussing the implications of their findings regarding boundedness and continuity. There is a recognition that only constant solutions appear to be bounded, but the reasoning behind the continuity of solutions for y''=0 remains unclear, with some expressing confusion.

Contextual Notes

Participants are navigating the constraints of the homework problem, particularly focusing on the definitions of boundedness and continuity in the context of the solutions they have derived.

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Homework Statement



Find the general solution of: y''+(1/x)y'=0
and show that only constant solutions are bounded.

Homework Equations





The Attempt at a Solution



integrating factor say a=e^(int(1/x)dr)=x
so xy''+y'=0. so (xy')'=0
integrate both sides: xy'=c (c is a constant)
integrate again: y=cln(x)+d (d is a constant)

but i don't know how to show that only constant solutions are bounded.
Thank you
 
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Hi sara_87! :smile:
sara_87 said:
Find the general solution of: y''+(1/x)y'=0
and show that only constant solutions are bounded.

y=cln(x)+d (d is a constant)

but i don't know how to show that only constant solutions are bounded

But you're there

ln(x) is unbounded, isn't it? :wink:
 
Oh right so this means only the solutions y=d can be bounded, right?
Also, there's a similar question:
find the general solution of: y''=0 and show that only constant solutions are continuous.

general solution i found to be: y=cx+d (again c and d are constants)
but in this case, why can only constant solutions be continuous?
 
sara_87 said:
find the general solution of: y''=0 and show that only constant solutions are continuous.

general solution i found to be: y=cx+d (again c and d are constants)
but in this case, why can only constant solutions be continuous?

dunno :confused:

must be a misprint :redface:
 
:)
It's not a misprint.
Never mind.
Thank you.
 

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