Power Series Solution for Differential Equation Near x0=1

In summary, the homework equation has a power series solution near x0=1. The solution is y=a0y1(x)+a1y2(x).
  • #1
pinkbabe02
10
0
differential equation help!

Homework Statement



(1+2x-x^2)y''-6xy'-6y=0 find power series solution of the equation near x0=1
(a)show the recurrence relation for an,
(b)derive a formula for an in terms of a0 and a1, and
(c)show the solution in the form y=a0y1(x)+a1y2(x)

Homework Equations





The Attempt at a Solution


I`ll attach the word file I typed it up in if that is easier to read...
(1+2x-x^2 ) y^''-6xy^'-6y=0, x_0=1
Let…
y=∑_(n=0)^∞▒〖a_n x^n 〗
y^'=∑_(n=1)^∞▒〖〖na〗_n x^(n-1) 〗
y^''=∑_(n=2)^∞▒〖n(n-1)a_n x^(n-2) 〗
(1+2x-x^2 ) ∑_(n=2)^∞▒〖n(n-1)a_n x^(n-2) 〗-6x∑_(n=1)^∞▒〖〖na〗_n x^(n-1) 〗-6∑_(n=0)^∞▒〖a_n x^n 〗=0
∑_(n=2)^∞▒〖n(n-1)a_n x^(n-2) 〗+∑_(n=2)^∞▒〖2n(n-1) a_n x^(n-1)-∑_(n=2)^∞▒〖n(n-1)a_n x^n 〗〗-∑_(n=1)^∞▒〖〖6na〗_n x^n 〗-∑_(n=0)^∞▒〖〖6a〗_n x^n 〗=0
∑_(n=0)^∞▒〖(n+2)(n+1)a_(n+2) x^n 〗+∑_(n=1)^∞▒〖2(n+1)(n) a_(n+1) x^n-∑_(n=2)^∞▒〖n(n-1)a_n x^n 〗〗-∑_(n=1)^∞▒〖〖6na〗_n x^n 〗-∑_(n=0)^∞▒〖〖6a〗_n x^n 〗=0
∑_(n=0)^∞▒〖[(n+2)(n+1) a_(n+2)-〖6a〗_n ] x^n 〗+∑_(n=1)^∞▒〖[2(n+1)(n) a_(n+1)-〖6na〗_n ] x^n-∑_(n=2)^∞▒〖n(n-1)a_n x^n 〗〗=0
I can turn the second term into n=0 since when n=0, the value equals 0 anyhow…the same goes for the third term (when n=0, 1 the value is 0), so we have…
∑_(n=0)^∞▒[(n+2)(n+1) a_(n+2)-〖6a〗_n ┤ +2(n+1)(n) a_(n+1)-〖6na〗_n-n(n-1)a_n 〖]x〗^n=0
∑_(n=0)^∞▒〖[(n+2)(n+1) a_(n+2)+(2n(n+1)) a_(n+1)+(-6-6n-n(n-1))a_n ] x^n=0〗
This is where I am stuck. I don’t know how to find the recurrence relation since I have a_n,a_(n+1),and a_(n+2). If someone could give me a hint that would be extremely helpful.
[STRIKE][STRIKE][/STRIKE][/STRIKE]
 

Attachments

  • problem 3.doc
    142.5 KB · Views: 153
Physics news on Phys.org
  • #2


Are you sure you copied the original differential equation down correctly?
 
  • #3


Yes I just double checked it again and that`s what the problem states.
 
  • #4


Your work looks good so far. If you simplify the last term in the coefficient, you get
[tex](n+2)(n+1) a_{n+2}+2n(n+1) a_{n+1}-(n+2)(n+3)a_n = 0[/tex]
This is a perfectly fine recurrence relation. Are you familiar with any techniques on how to solve one like this?

You might try writing out the first few terms and see if you can spot a pattern again.
 
  • #5


That`s what I had originally also but when I redid it, I saw that in this case x0=1 so the summation has (x-1) instead of x. then for my final recurrence relation, i have...(i attached the file)
 

Attachments

  • recurrence relation.doc
    29.5 KB · Views: 140

1. What are differential equations and why are they important?

Differential equations are mathematical equations that describe the relationship between a function and its derivatives. They are important because they are used to model real-life phenomena in many fields such as physics, engineering, economics, and biology. They allow us to make predictions and solve problems that would otherwise be difficult or impossible to solve.

2. What are the different types of differential equations?

There are several types of differential equations, including ordinary differential equations (ODEs) and partial differential equations (PDEs). ODEs involve a single independent variable, while PDEs involve multiple independent variables. ODEs can be further classified as linear or nonlinear, and first-order or higher-order, depending on the form of the equation.

3. How do I solve a differential equation?

The method for solving a differential equation depends on its type and complexity. Some common techniques include separation of variables, substitution, and using an integrating factor. In some cases, numerical methods such as Euler's method or the Runge-Kutta method may be used to approximate a solution.

4. What are initial value problems and boundary value problems?

An initial value problem is a type of differential equation that requires the solution to pass through a given point at a specific value of the independent variable. A boundary value problem, on the other hand, specifies conditions for the solution at multiple points. The techniques for solving these types of problems may differ, and it is important to identify which type of problem you are dealing with before attempting to solve it.

5. Are there any applications of differential equations in the real world?

Yes, there are countless applications of differential equations in the real world. They are used to model the movement of objects, the flow of fluids, the spread of diseases, and many other phenomena. They are also used in engineering to design and optimize systems, such as in control theory and signal processing.

Similar threads

  • Calculus and Beyond Homework Help
Replies
2
Views
640
  • Calculus and Beyond Homework Help
Replies
8
Views
925
  • Calculus and Beyond Homework Help
Replies
8
Views
1K
  • Calculus and Beyond Homework Help
Replies
6
Views
225
  • Calculus and Beyond Homework Help
Replies
5
Views
1K
  • Calculus and Beyond Homework Help
Replies
6
Views
677
  • Calculus and Beyond Homework Help
Replies
3
Views
495
  • Calculus and Beyond Homework Help
Replies
5
Views
472
  • Calculus and Beyond Homework Help
Replies
14
Views
1K
  • Calculus and Beyond Homework Help
Replies
2
Views
833
Back
Top