Troubleshooting Reduction of Order Equations: Where Did I Go Wrong?

  • Thread starter Thread starter Destroxia
  • Start date Start date
  • Tags Tags
    Reduction
Click For Summary
SUMMARY

The discussion centers on troubleshooting the reduction of order method for the differential equation t²y'' - t(t+2)y' + (t+2)y = 0, with a known solution y₁(t) = t. The user initially encountered difficulties when transforming the equation into a first-order linear equation and applying an integrating factor. After re-evaluating their algebra, they identified a mistake in the distribution of terms, which led to confusion regarding the solvability of the integral. The correct approach involves substituting y₂(t) = v(t)y₁(t) and simplifying to obtain the solvable equation t³v'' - t³v' = 0.

PREREQUISITES
  • Understanding of second-order linear differential equations
  • Familiarity with the reduction of order technique
  • Knowledge of integrating factors in first-order linear equations
  • Basic algebraic manipulation skills
NEXT STEPS
  • Study the method of reduction of order in detail
  • Learn about integrating factors and their application in solving first-order linear equations
  • Practice solving second-order differential equations using substitution methods
  • Explore common mistakes in algebraic manipulation within differential equations
USEFUL FOR

Students and educators in mathematics, particularly those focusing on differential equations, as well as anyone seeking to improve their problem-solving skills in this area.

Destroxia
Messages
204
Reaction score
7

Homework Statement


t^2*y^'' -t(t+2)y^' + (t+2)y=0 , t>0; ysub1(t) = t

Homework Equations


Reduction of order:

A second solution is assumed to be of the form:

ysub2(t) = v(t)*ysub1(t)

The Attempt at a Solution



work.jpg


So, the algebra in the first part of the process seemed to be correct, as it canceled out all the "v" terms and left only derivatives of v. The problem seems to happen somewhere around when I turn it into a first order linear equation and attempt to multiply through by an integrating factor. As far as I, and a CAS are concerned, that integral at the end is not possible to take. This leaves the assumption that I completely goofed up my integrating factor. Where could I have gone wrong?
 
Physics news on Phys.org
RyanTAsher said:

Homework Statement


t^2*y^'' -t(t+2)y^' + (t+2)y=0 , t>0; ysub1(t) = t

Homework Equations


Reduction of order:

A second solution is assumed to be of the form:

ysub2(t) = v(t)*ysub1(t)

The Attempt at a Solution



work.jpg


So, the algebra in the first part of the process seemed to be correct, as it canceled out all the "v" terms and left only derivatives of v.
I don't think so. After substituting y2(t) = tv into the differential equation, and simplifying, I ended up with this equation:
##t^3v'' - t^3v' = 0##, which is pretty easy to solve.

I'm pretty confident that this is correct, as I went ahead to find ##y_2## and found that it satisfied the diff. eqn.

RyanTAsher said:
The problem seems to happen somewhere around when I turn it into a first order linear equation and attempt to multiply through by an integrating factor. As far as I, and a CAS are concerned, that integral at the end is not possible to take. This leaves the assumption that I completely goofed up my integrating factor. Where could I have gone wrong?
 
Okay, I re-did all my algebra and I made the mistake somewhere distributing in the middle term. Thank you for your help.
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
1K
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
4
Views
2K
Replies
2
Views
1K
Replies
7
Views
2K
Replies
9
Views
2K
Replies
3
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 9 ·
Replies
9
Views
1K