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Math Help - initial value problem

  1. #1
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    initial value problem

    Given that y''=y'+2y and that y(0)=0 and y(1)=1 Deduce that one of the initial value problems has a trivial solution.

    Please tell me how can I get the trivial answer. If we set y(0)=0 and y'(0)=0 we get the correct answer, but the answer is saying that y(0)=0 and y'(0)=1 is also trivial(!) which doesn't make sense to me.
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  2. #2
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    An IVP, if I am not mistaken, refers to an equation together with a SINGLE value. What you have there looks more like a boundary problem. In any case, it has two values, so it's not an IVP.

    Perhaps they mean to give you two IVPs with the same equation... ? In that case y(0)=0 is obviously the one with the trivial solution.
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  3. #3
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    Quote Originally Posted by immortality View Post
    Given that y''=y'+2y and that y(0)=0 and y(1)=1 Deduce that one of the initial value problems has a trivial solution.

    Please tell me how can I get the trivial answer. If we set y(0)=0 and y'(0)=0 we get the correct answer, but the answer is saying that y(0)=0 and y'(0)=1 is also trivial(!) which doesn't make sense to me.
    \displaystyle y(x)=\frac{e^{1-x}-e^{2x+1}}{1-e^3}


    \displaystyle y'(x)=\frac{(2e^{3x}+1)e^{1-x}}{e^3-1}

    \displaystyle y'(0)=\frac{(2e^{0}+1)e^{1}}{e^3-1}=\frac{3e}{e^3-1}\neq 1
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  4. #4
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    Quote Originally Posted by immortality View Post
    Given that y''=y'+2y and that y(0)=0 and y(1)=1 Deduce that one of the initial value problems has a trivial solution.
    You are given a boundary value problem. I don't know what "one of the initial value problems" means. One of what initial value problems? Certainly one possible initial value problem for this differential equation is "y''= y'+ 2y with y(0)= 0, y'(0)= 0". That uses the same equation and one of the given boundary values so perhaps that is what is meant.

    Please tell me how can I get the trivial answer. If we set y(0)=0 and y'(0)=0 we get the correct answer, but the answer is saying that y(0)=0 and y'(0)=1 is also trivial(!) which doesn't make sense to me.
    Last edited by mr fantastic; January 1st 2011 at 04:46 AM. Reason: Fixed a boldface tag.
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  5. #5
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    Quote Originally Posted by hatsoff View Post
    An IVP, if I am not mistaken, refers to an equation together with a SINGLE value. What you have there looks more like a boundary problem. In any case, it has two values, so it's not an IVP.
    An "initial value problem" for a second order equation would give a value of y and its derivative at a single value of the independent variable.

    Perhaps they mean to give you two IVPs with the same equation... ? In that case y(0)=0 is obviously the one with the trivial solution.
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