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Math Help - 1st order DE and difference equation.

  1. #1
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    Question 1st order DE and difference equation.

    Solve the following differential/difference equations and show whether they are convergent
    1st order DE and difference equation.-solve-following-differential.pdf
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  2. #2
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    Quote Originally Posted by nepmma View Post
    Solve the following differential/difference equations and show whether they are convergent
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Name:	Solve the following differential.pdf 
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    Please type your questions out so that we do not have to opeb attachments.

    What have you tried and where are you stuck?
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    [QUOTE=nepmma;585464]Solve the following differential/difference equations and show whether they are convergent

    a) dy/dx=-3x-9
    b) change in y at time t = -2(y at time (t-1))+12

    i am stuck on part b as it includes the time element
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  4. #4
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    [QUOTE=nepmma;585567]
    Quote Originally Posted by nepmma View Post
    Solve the following differential/difference equations and show whether they are convergent

    a) dy/dx=-3x-9
    dy= -2(x- 3)dx.

    b) change in y at time t = -2(y at time (t-1))+12

    i am stuck on part b as it includes the time element
    "Change in y" over what interval? \Delta t= 1?
    Then  y(t)- y(t-1)= -1y(t-1)+ 12 so that math]y(t)= -2y(t-1)+ 12[/tex].

    In order to solve that you would need to know y(t) over some initial interval, say t= 0 to t= 1.

    Given that y(t)= f(t) for t= 0 to t= 1, y(t)= 12- 2f(t) for t= 1 to 2, y(t)= 12- 24- 4f(t)= -12- 4f(t) for t= 2 to t= 3, y(t)= 12- (-24- 8f(t))= 36+ 4f(t) for t= 3 to 4, etc.
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