What is the Correct Solution for the Difference Equation yn+1=-0.9yn?

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Discussion Overview

The discussion centers around solving the difference equation yn+1=-0.9yn, specifically in terms of the initial value y0. Participants explore the validity of different expressions for the solution and clarify the implications of the forms presented in a textbook.

Discussion Character

  • Technical explanation, Debate/contested

Main Points Raised

  • One participant proposes that the solution is yn=(-0.9)ny0 and questions its correctness compared to the textbook's solution.
  • Another participant asserts that both the proposed solution and the textbook solution are equivalent.
  • A third participant references a mathematical property, stating that (ab)^n = a^n b^n, possibly to support the discussion of the solution forms.
  • It is noted that the textbook's expression clarifies the sign of the terms, indicating that even terms are positive and odd terms are negative.
  • One participant emphasizes the need to verify that the proposed solution satisfies the original difference equation.

Areas of Agreement / Disagreement

There is some agreement that the two forms of the solution are equivalent, but the discussion remains unresolved regarding the completeness of the proposed solution and its verification against the original equation.

Contextual Notes

The discussion highlights the importance of verifying solutions to difference equations and the potential for different representations to convey additional information about the behavior of the sequence.

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Solve the difference equation yn+1=-0.9yn in terms of the initial value y0.

y1=-0.9y0
y2=-0.9y1=(-0.9)2y0
yn=(-0.9)ny0
Is this the answer? Because the answer in the textbook says yn=(-1)n(0.9)ny0. Please help.
 
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Your solution and the solution in your textbook are the same.
 
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[tex](ab)^n= a^n b^n[/tex]
 
The textbook wrote it that way to make it clear that even terms are positive and odd terms are negative.
 
And, as I pointed out in your previous thread, you are not finished until you have shown that your solution does satisfy the equation. If yn= (-0.9)ny0 then -0.9yn= -0.9((-0.9)ny0)= (-0.9)n+1y0= yn+1.
 

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