Recent content by Jack Jenkins

  1. J

    Finding roots to a recursively defined polynomial of degree n

    Hi everyone, sorry for the long delay I had the flu! All better now. I actually managed to get a directed study at my college approved that looks into this problem. What I'm concentrating on are the fact that certain numbers, such as 1, sqrt(2), sqrt(3), and (1+sqrt(5))/2 (the golden ratio)...
  2. J

    Existence of a function for the n-th prime

    There is a function \pi(x) that takes the natural numbers as its input and outputs the number of primes less than or equal to x. There are some nice properties of this function. For instance, the growth rate as x approaches infinity approaches x/lnx
  3. J

    Finding roots to a recursively defined polynomial of degree n

    Oops indeed! Math and the flu don't mix well. Once I'm feeling better I'll run through some more possibilities using the "family" of equalities above; I bet that there are other ways to represent P(n) as some easily tractable formula of "smaller" P(n)'s. Unfortunately, it seems that we're left...
  4. J

    Finding roots to a recursively defined polynomial of degree n

    to extend further, \begin{align*} P(n) &= xP(n-1) - P(n-2) \\ &= x\left( xP(n-2) - P(n-3) \right) - P(n-2) \\ &= (x^2-1)P(n-2) - xP(n-3) &= (x^3-x-1)P(n-3)-(x^2-1)P(n-2) \end{align*} and we could continue to extend this procedure to obtain as many repeated roots as we like.
  5. J

    Finding roots to a recursively defined polynomial of degree n

    Thank you all for your constructive comments! @coolul007, you're right, there do appear to be roots that occur over and over again, not only 0 and ±1 for n odd or even respectively, but for the square roots of certain integer numbers. For example, P(n), n=4,8,12,16 is zero at x=±\sqrt{2}...
  6. J

    Finding roots to a recursively defined polynomial of degree n

    Hello all, I have a series of polynomials P(n), given by the recursive formula P(n)=xP(n-1)-P(n-2) with initial values P(0)=1 and P(1)=x. P(2)=xx-1=x2-1 P(3)=x(x2-1)-(x)=x3-2x ... I am confident that all of the roots of P(n) lie on the real line. So for P(n), I hope to find these roots. I...
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