Solve Recursive Function: A_{n+1}= (8/9)A_n

In summary, to solve the recursive function A_{n+1} = (8/9)A_{n} + (24/9)*(20/9)^n for a closed formula, first solve the homogenous equation and then write a solution as A{n}= A*(8/9)^n + B * (20/9)^n. Plug this solution into the original equation to find B, and then use n=0 to find A.
  • #1
wimma
38
0

Homework Statement



Solve the recursive function:

A_{n+1} = (8/9)A_{n} + (24/9)*(20/9)^n

We want a closed formula for A_n


Homework Equations



I'm just doing this to work out the surface area of the Menger Sponge.

I know the formula's probably out there, but I get this recursive formula and I don't know how to solve it.

The Attempt at a Solution



I tried getting it in terms of A_{0}, which is 6, but I couldn't seem to simplify it... please help?!
 
Physics news on Phys.org
  • #2
First solve the homogenous equation, i.e A_{n+1}=8/9 A_{n}, then write a solution as:
A{n}= A*(8/9)^n + B * (20/9)^n
plug this solution to the equation to find B, and then plug n=0 A{0} to find A.
 

1. What is a recursive function?

A recursive function is a function that calls itself until it reaches a base case, which is a condition that stops the function from calling itself again. This allows the function to solve complex problems by breaking them down into smaller and simpler subproblems.

2. What is the formula for the recursive function An+1 = (8/9)An?

The formula for this recursive function is An+1 = (8/9)An, where An represents the value of the function at the nth term and An+1 represents the value at the (n+1)th term.

3. How do you solve a recursive function?

To solve a recursive function, you need to first identify the base case, which is the condition that will stop the function from calling itself again. Then, you can use the formula to calculate the value of the function at each term until you reach the base case. Finally, you can substitute the values back into the formula to get the solution.

4. What is the initial value for the recursive function A0?

The initial value for the recursive function A0 is usually given in the problem or can be determined by the base case. In some cases, it may be assumed to be 1 or 0, but it is important to check with the problem statement to determine the actual initial value.

5. What are some real-life applications of recursive functions?

Recursive functions have many practical applications in computer science, mathematics, and other fields. Some examples include calculating the factorial of a number, finding the nth term in a sequence, and traversing data structures such as trees and graphs. They are also used in algorithms for sorting, searching, and other problem-solving techniques.

Similar threads

  • Calculus and Beyond Homework Help
Replies
8
Views
1K
  • Calculus and Beyond Homework Help
2
Replies
51
Views
4K
  • General Math
Replies
4
Views
2K
  • Calculus and Beyond Homework Help
Replies
3
Views
558
  • Set Theory, Logic, Probability, Statistics
Replies
2
Views
3K
  • Calculus and Beyond Homework Help
Replies
15
Views
1K
Replies
1
Views
698
  • Calculus and Beyond Homework Help
Replies
7
Views
2K
  • Differential Equations
Replies
7
Views
2K
  • Calculus and Beyond Homework Help
Replies
3
Views
1K
Back
Top