Solve first order difference equation!

  • Thread starter toofle
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  • #1
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Homework Statement


Solve the first order difference equation.

Homework Equations


x[n] - x[n-1] = n(n+1)/2
x[1] = 1



The Attempt at a Solution


Homogenous solution:
Characteristic equation:
r - 1 = 0 <=> r = 1
=> yhn = C * 1^n = C

Particular solution:
ypn = ?
I'm supposed to do some intelligent guess here. n(n+1)/2 is a polynomial of degree 2 and dosnt exist in yhn so i should be something like An(n+1) or An^2+Bn but Ican't get anything to work.
 

Answers and Replies

  • #2
Dick
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I would guess a polynomial of order 1 degree higher than n(n+1)/2. Say An^3+Bn^2+Cn.
 

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