Solve 2nd Order DE: Finding 2nd Solution w/ Reduction of Order

  • Thread starter Punchlinegirl
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In summary, to find a second solution of the given differential equation t^2y"-4ty'+6y=0, t>0 and y_1(t)=t^2, we can use reduction of order. After putting the equation in standard form, substituting y=v(t)t^2, and simplifying, we get t^2v"(t)+6t^2v(t)-6v(t) as our new equation. From here, we can easily find the second solution by setting t^2v"(t)+6t^2v(t)-6v(t)=0.
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Punchlinegirl
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Use reduction of order to find a second solution of the given differential equation
t^2y"-4ty'+6y=0 t>0 y_1(t)=t^2

first I put in in the standard form
y"-4/ty'+6/t^2y =0
then y= v(t)t^2
y'=v'(t)t^2+v(t)2t
y"=y"(t)t^2+v'(t)2t+v'(t)2t+v(t)2 = t^2v"(t)+4tv'(t)+2v(t)
putting these into the original equation gives me
t^2v"(t)+4tv'(t)+2v(t)-4tv'(t)-8v(t)+6t^2v(t)
simplifying gives me
t^2v"(t)+6t^2v(t)-6v(t)
I don't know what to do from here. can someone please help?
 
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  • #2
Punchlinegirl said:
Use reduction of order to find a second solution of the given differential equation
t^2y"-4ty'+6y=0 t>0 y_1(t)=t^2

first I put in in the standard form
y"-4/ty'+6/t^2y =0
then y= v(t)t^2
y'=v'(t)t^2+v(t)2t
y"=y"(t)t^2+v'(t)2t+v'(t)2t+v(t)2 = t^2v"(t)+4tv'(t)+2v(t)
putting these into the original equation gives me
t^2v"(t)+4tv'(t)+2v(t)-4tv'(t)-8v(t)+6t^2v(t)
The is wrong. You have added 6y but it should be [itex]\frac{6}{t^2}y[/itex], just 6v, not 6t^3 v.
You should have
[tex]t^2v"+ 4tv'+ 2v- 4tv'- 8v+ 6v= t^2v"= 0[/itex]
That should be easy!

Simplifying gives me
t^2v"(t)+6t^2v(t)-6v(t)
I don't know what to do from here. can someone please help?
 

1. What is a second-order differential equation?

A second-order differential equation is a mathematical equation that involves the second derivative of a function. It is commonly used to model physical phenomena and is an important concept in calculus and engineering.

2. How do you solve a second-order differential equation?

The general method for solving a second-order differential equation is to first reduce it to a first-order equation by introducing a new variable. Then, the equation can be solved using various techniques such as separation of variables, variation of parameters, or the method of undetermined coefficients.

3. What is reduction of order?

Reduction of order is a technique used to solve a second-order differential equation by reducing it to a first-order equation. This is done by introducing a new variable and substituting it into the original equation, which results in a first-order equation that can be solved using standard methods.

4. Why is it important to find a second solution to a second-order differential equation?

In some cases, a second solution is needed to fully describe the behavior of a physical system or to satisfy boundary conditions. It can also be used to check the validity of the first solution or to find a particular solution that meets certain criteria.

5. What are some common applications of second-order differential equations?

Second-order differential equations are commonly used in physics, engineering, and other fields to model systems such as oscillating springs, electrical circuits, and population growth. They are also used in economics, biology, and other sciences to describe various phenomena.

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