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Math Help - simple math pattern

  1. #1
    Devin Brugger
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    Cool simple math pattern

    what is the pattern of 0,5,20,48,80 please help devin
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    Quote Originally Posted by Devin Brugger View Post
    what is the pattern of 0,5,20,48,80 please help devin
    a_n=-(1/2)x^4+(11/2)x^3-(31/2)x^2+(41/2)x-10
    So,
    a_0=0
    a_1=5
    a_2=20
    a_3=48
    a_4=80
    ---
    It follows the rule of a quartic plynomial.
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  3. #3
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by Devin Brugger View Post
    what is the pattern of 0,5,20,48,80 please help devin
    I can't find a pattern for 0, 5, 20,... but I can find one for 0, 6, 20, 48, 80

    Typo?

    -Dan
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  4. #4
    dan
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    ok PH, i'm impressed....how in the world did you come up with that?? what is the strategy to finding patterns..??
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  5. #5
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    Quote Originally Posted by dan View Post
    ok PH, i'm impressed....how in the world did you come up with that?? what is the strategy to finding patterns..??
    Thank you, I am humanities gift from the gods I cannot tell you how I found that.

    Okay, okay I be honest.

    I used something called "method of least squares" for polynomials. It works for other class of functions. When I use this I looks whether or not this function is "good" looking. Meaning are the coefficients nice or ugly? If nice like here I assume that is the pattern. CaptainBlank referrs to it as the "Lagrange Interpolating polynomial".

    In fact I can prove that given a sequence:
    a_0,a_1,...,a_(n-1)
    We can find a unique polynomial having a degree up to (n-1) with precisely satisfies this equation. (The prove is based on being able to solve a system of linear equations).
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  6. #6
    Grand Panjandrum
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    Quote Originally Posted by ThePerfectHacker View Post
    a_n=-(1/2)x^4+(11/2)x^3-(31/2)x^2+(41/2)x-10
    So,
    a_0=0
    a_1=5
    a_2=20
    a_3=48
    a_4=80
    ---
    It follows the rule of a quartic plynomial.
    If you start from 0, then the first element in the sequence would be -10
    from your quartic. You mean:

    a_1=0
    a_2=5
    a_3=20
    a_4=48
    a_5=80

    RonL
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  7. #7
    Grand Panjandrum
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    Quote Originally Posted by ThePerfectHacker View Post
    Thank you, I am humanities gift from the gods I cannot tell you how I found that.

    Okay, okay I be honest.

    I used something called "method of least squares" for polynomials. It works for other class of functions. When I use this I looks whether or not this function is "good" looking. Meaning are the coefficients nice or ugly? If nice like here I assume that is the pattern. CaptainBlank referrs to it as the "Lagrange Interpolating polynomial".
    No I don't, the Lagange interpolating polynomial is constructed to exactly
    go through the points. It just so happens that a least squares polynomial
    fit of a degree n-1 polynomial to a squence of n points must also go through
    the points and so in practice is identical to the Lagrange polynomial, but
    they differ in their method of construction.

    Here the least square and the Lagrange polynomials are the same but the
    distinction between them remains as it lies in their methods of construction.

    RonL

    RonL
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  8. #8
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by ThePerfectHacker View Post
    a_n=-(1/2)x^4+(11/2)x^3-(31/2)x^2+(41/2)x-10
    So,
    a_0=0
    a_1=5
    a_2=20
    a_3=48
    a_4=80
    ---
    It follows the rule of a quartic plynomial.
    The problem is that this sort of solution is almost never the solution to this kind of problem. Odds are there is some method to construct the terms of the series and your polynomial will not predict the next one. (I tried this once as the solution to a "Math Challenge" and the professor's granted that I had found a solution, just not the right one. ) Though I will grant it was a nice piece of work.

    -Dan
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  9. #9
    Grand Panjandrum
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    Quote Originally Posted by topsquark View Post
    The problem is that this sort of solution is almost never the solution to this kind of problem. Odds are there is some method to construct the terms of the series and your polynomial will not predict the next one. (I tried this once as the solution to a "Math Challenge" and the professor's granted that I had found a solution, just not the right one. )
    Which is why I usually respond what is the next term questions with what
    would you like it to be.


    RonL
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  10. #10
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by CaptainBlack View Post
    Which is why I usually respond what is the next term questions with what
    would you like it to be.


    RonL
    That's two double posts in one day for you, Captain. Is your evil twin on the computer again?

    -Dan
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  11. #11
    Grand Panjandrum
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    Quote Originally Posted by topsquark View Post
    That's two double posts in one day for you, Captain. Is your evil twin on the computer again?

    -Dan
    It's the sluggishness of the world wide wait (at least at work in the
    lunch hour ) results in me editing a post while the original is uploading
    without noticing, then hitting submit again

    Its also a type of double posting I don't mind too much when others do
    it. Near identical posts in the same thread (of forum) are usually finger
    trouble, best way to deal with them is to just delete the duplicate.

    RonL
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