Differential Equations: Second Order Equations

If you use that to try to find a linear differential equation with e^{2t} and e^{(-t+ 1)} as solutions you will find that the characteristic equation is (r- 2)(r- (-1+ 1)= (r- 2)(r)= 0 which means that the linear differential equation is y''- 2y'+ 0y= y''- 2y'= (D^2- 2D)y= 0 where D is the "derivative operator" so y''- 2y'= Dy'- 2Dy= 0 which is a first order linear differential equation. That is, in order to have e^{2t} and
  • #1
peace-Econ
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0

Homework Statement



Find a second order differential ewuation for which three functions y=2e^-t, y=2te^-t, y=e^(-t+1) are solutions.

Homework Equations





The Attempt at a Solution

 
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  • #2
Since you didn't show us what you have tried, instead of answering your question directly, I will ask you this:

Can you solve this de:

y'' - 4y' + 4y = e2t

and if so, what method would you use?

Hint: This isn't an idle question.
 
  • #3
peace-Econ said:

Homework Statement



Find a second order differential ewuation for which three functions y=2e^-t, y=2te^-t, y=e^(-t+1) are solutions.

Homework Equations





The Attempt at a Solution

If those functions were independent, this would be impossible but [itex]e^{-t+ 1}= e^{-t}e^1= e e^{-t}[/itex], a constant times [itex]e^{-t}[/itex] so you really have only two independent solutions.

Do you know what the "characteristic equation" of a linear differential with constant coefficients is? Such an equation will have [itex]e^{ax}[/itex] and [itex]e^{bx}[/itex] as independent solutions if and only if its characteristic equation is [itex](r- a)(r- b)= 0[/itex].
 
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1. What is the definition of a second order differential equation?

A second order differential equation is an equation that contains a second derivative of an unknown function. It is typically written in the form of y'' = f(x,y,y'), where y' is the first derivative and y'' is the second derivative.

2. What is the difference between a linear and a nonlinear second order differential equation?

A linear second order differential equation has the form y'' + p(x)y' + q(x)y = g(x), where p(x) and q(x) are functions of x and g(x) is a function of x. A nonlinear second order differential equation is any equation that cannot be written in this form.

3. How do you solve a second order differential equation?

The method for solving a second order differential equation depends on the type of equation. For linear equations, it can be solved using techniques such as separation of variables, integrating factors, or series solutions. Nonlinear equations may require numerical methods or approximation techniques to find solutions.

4. What are the applications of second order differential equations?

Second order differential equations are used to model many physical phenomena, such as motion, oscillations, and electrical circuits. They are also commonly used in engineering, economics, and other fields to analyze and predict behavior of systems.

5. Can a second order differential equation have more than one solution?

Yes, a second order differential equation can have multiple solutions. In fact, the general solution to a second order differential equation will typically include two arbitrary constants, allowing for an infinite number of solutions.

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