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Thread: Recursive formula

  1. #1 Recursive formula 
    Forum Sophomore biohazard87's Avatar
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    I have been working on this problem for about 5 days now and I still can't figure out the answer. One of my friends at school even asked someone from his work who is an electrical engineer that minored in math and he couldn't get it. the given series is 2,1,1,(15/7),390...

    that is two, one, one, fifteen halfs, three hundred ninty...

    if anyone can figure out the pattern and/or the formula for this series I would greatly appreciate it. I know that it is a sud n+1= ( )a sub n
    but out side of that I have no idea what the solution could be. Any help on this would be greatly appreciated, again. Thanks.


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  3. #2  
    Forum Sophomore Absane's Avatar
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    Is there enough information??


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  4. #3  
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    fifteen halves or fifteen sevenths?
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  5. #4  
    Forum Professor river_rat's Avatar
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    There is no unique way of solving these problems biohazard unless you give us more information. For example you can interpolate a polynomial p(n) such that a<sub>n+1</sub> = p(n) a<sub>n</sub> etc. etc. etc.
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  6. #5  
    Forum Sophomore biohazard87's Avatar
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    Quote Originally Posted by river_rat
    There is no unique way of solving these problems biohazard unless you give us more information. For example you can interpolate a polynomial p(n) such that a<sub>n+1</sub> = p(n) a<sub>n</sub> etc. etc. etc.
    I think that is the way that it is supposed to bve done. But any solution to this problom would be helpful. In any form.


    Quote Originally Posted by Harold14370
    fifteen halves or fifteen sevenths?
    15/2 sorry. that is fifteen halfs. 7.5 is what I was thinking when I put that is. Sorry.
    Noodles happen when you kiss a stranger in the alps.

    Mi padre tiene un impala.
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  7. #6  
    Forum Sophomore biohazard87's Avatar
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    Please. Anything, even just a hint as to a pattern that I could do. something like an+1 = an*x^n or something. I still cant get it, and neither can anyone in my class but the teacher wont tell us until someone can bring in an answer for somewhere.
    Noodles happen when you kiss a stranger in the alps.

    Mi padre tiene un impala.
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  8. #7  
    Forum Professor river_rat's Avatar
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    have you looked up interpolating polynomials?
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  9. #8  
    Forum Sophomore Absane's Avatar
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    Quote Originally Posted by biohazard87
    Please. Anything, even just a hint as to a pattern that I could do. something like an+1 = an*x^n or something. I still cant get it, and neither can anyone in my class but the teacher wont tell us until someone can bring in an answer for somewhere.
    Honestly you could try to think of a bunch of things. As River suggested, just make a polynomial that passes through all the points to guess what the next point is. However there is no guarantee that will even be close to the answer you teacher is thinking.
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  10. #9  
    Forum Professor river_rat's Avatar
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    I can almost assure you it won't be the formula your teacher has, but you have not been given the entire sequence anyway so what would the "correct" formula be?
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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  11. #10  
    Forum Sophomore biohazard87's Avatar
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    Quote Originally Posted by river_rat
    have you looked up interpolating polynomials?
    I am sorry, what is that and where would I look it up?
    Noodles happen when you kiss a stranger in the alps.

    Mi padre tiene un impala.
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